Principal Risks

When you sell Fund shares, they may be worth less than what you paid for them. Consequently, you can lose money by investing in the Fund. No assurance can be given that the Fund will achieve its objective, and investment results may vary substantially over time and from period to period. An investment in the Fund is not appropriate for all investors.

Counterparty Risk. A counterparty (the other party to a transaction or an agreement or the party with whom the Fund executes transactions) to a transaction with the Fund may be unable or unwilling to make timely principal, interest or settlement payments, or otherwise honor its obligations.

Credit Risk. The issuers of certain securities or the counterparties of a derivatives contract or repurchase contract might be unable or unwilling (or perceived as being

3

unable or unwilling) to make interest and/or principal payments when due, or to otherwise honor its obligations. Debt securities are subject to the risk of non-payment of scheduled interest and/or principal. Non-payment would result in a reduction of income to the Fund, a reduction in the value of the obligation experiencing non-payment and a potential decrease in the Net Asset Value (“NAV”) of the Fund.

Currency Risk. Fluctuations in exchange rates will adversely affect the value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

Debt Securities Risk. The value of debt securities typically changes in response to various factors, including, by way of example, market-related factors (such as changes in interest rates or changes in the risk appetite of investors generally) and changes in the actual or perceived ability of the issuer (or of issuers generally) to meet its (or their) obligations. During periods of rising interest rates, debt securities generally decline in value. Conversely, during periods of falling interest rates, debt securities generally rise in value. This kind of market risk is generally greater for Funds investing in debt securities with longer maturities .

Derivatives Risk. Derivatives Risk is a combination of several risks, including the risks that: (1) an investment in a derivative instrument may not correlate well with the performance of the securities or asset class to which the Fund seeks exposure, (2) derivative contracts, including options, may expire worthless and the use of derivatives may result in losses to the Fund, (3) a derivative instrument entailing leverage may result in a loss greater than the principal amount invested, (4) derivatives not traded on an exchange may be subject to credit risk, for example, if the counterparty does not meet its obligations (see also “Counterparty Risk”), and (5) derivatives not traded on an exchange may be subject to liquidity risk and the related risk that the instrument is difficult or impossible to value accurately. As a general matter, when a Fund establishes certain derivative instrument positions, such as certain futures, options and forward contract positions, it will segregate liquid assets (such as cash, U.S. Treasury bonds or commercial paper) equivalent to the Fund’s outstanding obligations under the contract or in connection with the position. In addition, recent legislation has called for a new regulatory framework for the derivatives market. The impact of the new regulations are still unknown, but has the potential to increase the costs of using derivatives, may limit the availability of some forms of derivatives or the Fund’s ability to use derivatives, and may adversely affect the performance of some derivative instruments used by the Fund as well as the Fund’s ability to pursue its investment objective through the use of such instruments.

Emerging Markets Risk. Investing in securities of issuers tied economically to emerging markets entails all of the risks of investing in securities of non-U.S. issuers detailed below under “Non-U.S. Securities Risk” to a heightened degree. These heightened risks include: (i) greater risks of expropriation, confiscatory taxation, nationalization, and less social, political and economic stability; (ii) the smaller size of the markets for such securities and a lower volume of trading, resulting in lack of liquidity and in price volatility; (iii) greater fluctuations in currency exchange rates; and (iv) certain national policies that may restrict a Fund’s investment opportunities, including restrictions on investing in issuers or industries deemed sensitive to relevant national interests.

Equity Securities Risk. Because it may purchase common stocks and other equity securities, the Fund is subject to the risk that stock prices will fall over short or long periods of time. In addition, common stocks represent a share of ownership in a company, and rank after bonds and preferred stock in their claim on the company’s assets in the event of bankruptcy.

ETF Risk. The price movement of an ETF may not exactly track the underlying index and may result in a loss. In addition, shareholders bear both their proportionate share of the Fund’s expenses and similar expenses of the underlying investment company when the Fund invests in shares of another investment company.

Focused Investment Risk. The Fund’s investments in Senior Loans arranged through private negotiations between a Borrower and several financial institutions may expose the Fund to risks associated with the financial services industry. The financial services industry is subject to extensive government regulation, which can limit both the amounts and types of loans and other financial commitments financial services companies can make and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change. Because financial services companies are highly dependent on short-term interest rates, they can be adversely affected by downturns in the U.S. and foreign economies or changes in banking regulations. Losses resulting from financial difficulties of borrowers can negatively affect financial services companies. The financial services industry is currently undergoing relatively rapid change as existing distinctions between financial service segments become less clear. This change may make it more difficult for the Adviser to analyze investments in this industry. Additionally, the recently increased volatility in the financial markets and implementation of the recent financial reform legislation may affect the financial services industry as a whole in ways that may be difficult to predict.

Hedging Risk. Although intended to limit or reduce investment risk, hedging strategies may also limit or reduce the potential for profit. There is no assurance that hedging strategies will be successful.

High Yield Debt Securities Risk. Below investment grade securities or unrated securities of similar credit quality (commonly known as “high yield securities” or “junk securities”) are more likely to default than higher rated securities. The Fund’s ability to invest in high-yield debt securities generally subjects the Fund to greater risk than securities with higher ratings. Such securities are regarded by the rating organizations as predominantly speculative with respect to capacity to pay interest and repay principal in accordance with the terms of the obligation. The market value of these securities is more sensitive to corporate developments and economic conditions and can be volatile. Market conditions can diminish liquidity and make accurate valuations difficult to obtain.

4

Highland Funds I Prospectus

October 31, 2013

Illiquid and Restricted Securities Risk. The Adviser may not be able to sell illiquid or restricted securities at the price it would like or may have to sell them at a loss. Securities of non-U.S. issuers and emerging markets securities in particular, are subject to greater liquidity risk.

Interest Rate Risk. When interest rates decline, the value of fixed rate securities already held by the Fund can be expected to rise. Conversely, when interest rates rise, the value of existing fixed rate portfolio securities can be expected to decline. A fund with a longer average portfolio duration will be more sensitive to changes in interest rates than a fund with a shorter average portfolio duration. However, the Fund will primarily invest in floating rate obligations, including Senior Loans, the rates on which periodically adjust with changes in market interest rates. Consequently, the Fund’s exposure to fluctuations in interest rates will generally be limited to the time that the interest rates on the Senior Loans in its portfolio are reset.

Leverage Risk. The Fund is authorized to borrow in an amount up to 33 1/3% of its total assets (including the amount borrowed). The use of leverage for investment purposes creates opportunities for greater total returns, but at the same time involves risks. Any investment income or gains earned with respect to the amounts borrowed that are in excess of the interest that is due on the borrowing will augment the Fund’s income. Conversely, if the investment performance with respect to the amounts borrowed fails to cover the interest on such borrowings, the value of the Fund’s shares may decrease more quickly than would otherwise be the case. Interest payments and fees incurred in connection with such borrowings will reduce the amount of net income available for payment to Fund shareholders.

Limited Information Risk. The types of Senior Loans in which the Fund will invest historically may not have been rated by a NRSRO, have not been registered with the SEC or any state securities commission, and have not been listed on any national securities exchange. Although the Fund will generally have access to financial and other information made available to the Lenders in connection with Senior Loans, the amount of public information available with respect to Senior Loans will generally be less extensive than that available for rated, registered or exchange-listed securities. As a result, the performance of the Fund and its ability to meet its investment objective is more dependent on the analytical ability of the Adviser than would be the case for an investment company that invests primarily in rated, registered or exchange-listed securities.

Management Risk. The Fund relies on the Adviser’s ability to achieve its investment objective. The Adviser may be incorrect in its assessment of the intrinsic value of companies whose securities the Fund holds, which may result in a decline in the value of Fund shares and failure to achieve its investment objective. The Fund’s portfolio managers use qualitative analyses and/or models. Any imperfections or limitations in such analyses and models could affect the ability of the portfolio managers to implement strategies.

Non-Diversification Risk . As a non-diversified fund for the purposes of the 1940 Act, the Fund may invest a larger portion of its assets in the securities of fewer issuers than a diversified fund. The Fund’s investment in fewer issuers may result in the Fund’s shares being more sensitive to the economic results of those issuers. An investment in the Fund could fluctuate in value more than an investment in a diversified fund.

Non-Payment Risk. Debt securities are subject to the risk of non-payment of scheduled interest and/or principal. Non-payment would result in a reduction of income to the Fund, a reduction in the value of the obligation experiencing non-payment and a potential decrease in the Net Asset Value (“NAV”) of the Fund.

Non-U.S. Securities Risk. Investments in securities of non-U.S. issuers involve certain risks not involved in domestic investments (for example, fluctuations in foreign exchange rates (for non-U.S. securities not denominated in U.S. dollars); future foreign economic, financial, political and social developments; nationalization; exploration or confiscatory taxation; smaller markets; different trading and settlement practices; less governmental supervision; and different accounting, auditing and financial recordkeeping standards and requirements) that may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies. These risks are magnified for investments in issuers tied economically to emerging markets, the economies of which tend to be more volatile than the economies of developed markets. In addition, certain investments in non-U.S. securities may be subject to foreign withholding taxes on interest, dividends, capital gains or other income. Those taxes will reduce the Fund’s yield on any such securities. See the “Taxation” section below.

Ongoing Monitoring Risk. On behalf of the several Lenders, the Agent generally will be required to administer and manage the Senior Loans and, with respect to collateralized Senior Loans, to service or monitor the collateral. Financial difficulties of Agents can pose a risk to the Fund. Unless, under the terms of the loan, the Fund has direct recourse against the Borrower, a Fund may have to rely on the Agent or other financial intermediary to apply appropriate credit remedies against a Borrower.

Payment-in-Kind Securities Risk. The value of payment-in-kind securities (“PIKs”) held by the Fund may be more sensitive to fluctuations in interest rates than other securities. PIKs pay all or a portion of their interest or dividends in the form of additional securities. Federal tax law requires that the interest on PIK bonds be accrued as income to the Fund regardless of the fact that the Fund will not receive cash until such securities mature. Since the income must be distributed to shareholders, the Fund may be forced to liquidate other securities in order to make the required distribution.

Portfolio Turnover Risk. High portfolio turnover will increase the Fund’s transaction costs and may result in increased realization of net short-term capital gains (which are taxable to shareholders as ordinary income when distributed to them), higher taxable distributions and lower after-tax performance.

Prepayment Risk. During periods of falling interest rates, issuers of debt securities may repay higher rate securities before their maturity dates. This may cause the Fund to lose potential price appreciation and to be forced to reinvest the

5

unanticipated proceeds at lower interest rates. This may adversely affect the NAV of the Fund’s shares.

Regulatory Risk. To the extent that legislation or state or federal regulators impose additional requirements or restrictions with respect to the ability of financial institutions to make loans in connection with highly leveraged transactions, the availability of Senior Loan interests for investment by the Fund may be adversely affected.

Risk of Substantial Redemptions. If substantial numbers of shares in the Fund were to be redeemed at the same time or at approximately the same time, the Fund might be required to liquidate a significant portion of its investment portfolio quickly to meet the redemptions. The Fund might be forced to sell portfolio securities at prices or at times when it would otherwise not have sold them.

Securities Lending Risk. The fund may make secured loans of its portfolio securities. Any decline in the value of a portfolio security that occurs while the security is out on loan is borne by the Fund, and will adversely affect performance. Also, there may be delays in recovery of securities loaned, losses in the investment of collateral, and loss of rights in the collateral should the borrower of the securities fail financially while holding the security.

Securities Market Risk. The value of securities owned by the Fund may go up or down, sometimes rapidly or unpredictably, due to factors affecting particular companies or the securities markets generally. A general downturn in the securities market may cause multiple asset classes to decline in value simultaneously. Many factors can affect this value and you may lose money by investing in the Fund.

Senior Loans Risk. The risks associated with Senior Loans are similar to the risks of below investment grade securities. Senior Loans and other debt securities are also subject to the risk of price declines and to increases in prevailing interest rates. The Fund’s investments in Senior Loans are typically below investment grade and are considered speculative because of the credit risk of their issuers. The secondary market for loans is generally less liquid than the market for higher grade debt. Less liquidity in the secondary trading market could adversely affect the price at which the Fund could sell a loan, and could adversely affect the NAV of the Fund’s shares. The volume and frequency of secondary market trading in such loans varies significantly over time and among loans.

Short Sales Risk. This is the risk of loss associated with any appreciation on the price of a security borrowed in connection with a short sale. The Fund may engage in short sales that are not made “against-the-box” (as defined under “Description of Principal Investments”), which means that the Fund may sell short securities even when they are not actually owned or otherwise covered at all times during the period the short position is open. Short sales that are not made “against-the-box” theoretically involve unlimited loss potential since the market price of securities sold short may continuously increase.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the FDIC or any other government agency. As with any mutual fund, there is no guarantee that the Fund will achieve its goal.

Risk/Return Bar Chart and Table for the Fund

The bar chart and the performance table below provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund’s Class A Shares from year to year and by showing how the Fund’s average annual returns for the Fund’s Class A, Class B, Class C and Class Z Shares compared to those of a broad measure of market performance. As with all mutual funds, the Fund’s past performance (before and after taxes) does not predict how the Fund will perform in the future. Both the chart and the table assume the reinvestment of dividends and distributions. The bar chart does not reflect the deduction of applicable sales charges for Class A Shares. If sales charges had been reflected, the returns for Class A Shares would be less than those shown below. The Fund is the successor to Highland Floating Rate Advantage Fund, a Delaware statutory trust, a closed-end interval fund with substantially similar investment objective, strategies, and policies (the “Predecessor Fund”). The performance of the Fund’s Class A, Class B, Class C and Class Z Shares provided in the chart and the table is that of the Predecessor Fund for all periods prior to June 13, 2011. Updated information on the Fund’s performance can be obtained by visiting https://www.highlandfunds.com/Funds———Performance/Mutual-Funds/Alternative-Investment/Floating-Rate-Opportunities or by calling 1-877-665-1287.

Annual Total Return ¹

(As of December 31 for Class A Shares)

The highest calendar quarter total return for Class A Shares of the Fund was 12.03% for the quarter ended September 30, 2009 and the lowest calendar quarter total return was (33.78)% for the quarter ended December 31, 2008.

6

Highland Funds I Prospectus

October 31, 2013

Principal Risks

When you sell Fund shares, they may be worth less than what you paid for them. Consequently, you can lose money by investing in the Fund. No assurance can be given that the Fund will achieve its objective, and investment results may vary substantially over time and from period to period. An investment in the Fund is not appropriate for all investors.

Counterparty Risk. A counterparty (the other party to a transaction or an agreement or the party with whom the Fund executes transactions) to a transaction with the Fund may be unable or unwilling to make timely principal, interest or settlement payments, or otherwise honor its obligations.

Credit Risk. The issuers of certain securities or the counterparties of a derivatives contract or repurchase contract might be unable or unwilling (or perceived as being unable or unwilling) to make interest and/or principal payments when due, or to otherwise honor its obligations. Debt securities are subject to the risk of non-payment of scheduled interest and/or principal. Non-payment would result in a reduction of income to the Fund, a reduction in the value of the obligation experiencing non-payment and a potential decrease in the Net Asset Value (“NAV”) of the Fund.

Currency Risk. Fluctuations in exchange rates will adversely affect the value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

Debt Securities Risk. The value of debt securities typically changes in response to various factors, including, by way of example, market-related factors (such as changes in interest rates or changes in the risk appetite of investors generally) and changes in the actual or perceived ability of the issuer (or of issuers generally) to meet its (or their) obligations. During periods of rising interest rates, debt securities generally decline in value. Conversely, during periods of falling interest rates, debt securities generally rise in value. This kind of market risk is generally greater for Funds investing in debt securities with longer maturities.

Derivatives Risk. Derivatives Risk is a combination of several risks, including the risks that: (1) an investment in a derivative instrument may not correlate well with the performance of the securities or asset class to which the Fund seeks exposure, (2) derivative contracts, including options, may expire worthless and the use of derivatives may result in losses to the Fund, (3) a derivative instrument entailing leverage may result in a loss greater than the principal amount invested, (4) derivatives not traded on an exchange may be subject to credit risk, for example, if the counterparty does not meet its obligations (see also “Counterparty Risk”), and (5) derivatives not traded on an exchange may be subject to liquidity risk and the related risk that the instrument is difficult or impossible to value accurately. As a general matter, when a Fund establishes certain derivative instrument positions, such as certain futures, options and forward contract positions, it will segregate liquid assets (such as cash, U.S. Treasury bonds or commercial paper) equivalent to the Fund’s outstanding obligations under the contract or in connection with the position. In addition, recent legislation has called for a new regulatory framework for the derivatives market. The impact of the new regulations are still unknown, but has the potential to increase the costs of using derivatives, may limit the availability of some forms of derivatives or the Fund’s ability to use derivatives, and may adversely affect the performance of some derivative instruments used by the Fund as well as the Fund’s ability to pursue its investment objective through the use of such instruments.

Emerging Markets Risk. Investing in securities of issuers tied economically to emerging markets entails all of the risks of investing in securities of non-U.S. issuers detailed below under “Non-U.S. Securities Risk” to a heightened degree. These heightened risks include: (i) greater risks of expropriation, confiscatory taxation, nationalization, and less social, political and economic stability; (ii) the smaller size of the markets for such securities and a lower volume of trading, resulting in lack of liquidity and in price volatility; (iii) greater fluctuations in currency exchange rates; and (iv) certain national policies that may restrict a Fund’s investment opportunities, including restrictions on investing in issuers or industries deemed sensitive to relevant national interests.

Equity Securities Risk. Because it purchases common stocks and other equity securities, the Fund is subject to the risk that stock prices will fall over short or long periods of time. In addition, common stocks represent a share of ownership in a company, and rank after bonds and preferred stock in their claim on the company’s assets in the event of bankruptcy.

ETF Risk. The price movement of an ETF may not exactly track the underlying index and may result in a loss. In addition, shareholders bear both their proportionate share of the Fund’s expenses and similar expenses of the underlying investment company when the Fund invests in shares of another investment company.

Hedging Risk. Although intended to limit or reduce investment risk, hedging strategies may also limit or reduce the potential for profit. There is no assurance that hedging strategies will be successful.

Illiquid and Restricted Securities Risk. The Adviser may not be able to sell illiquid or restricted securities at the price it would like or may have to sell them at a loss. Securities of non-U.S. issuers and emerging markets securities in particular, are subject to greater liquidity risk.

Interest Rate Risk. When interest rates decline, the value of fixed rate securities already held by the Fund can be expected to rise. Conversely, when interest rates rise, the value of existing fixed rate portfolio securities can be expected to decline. A fund with a longer average portfolio duration will be more sensitive to changes in interest rates than a fund with a shorter average portfolio duration.

Leverage Risk. The Fund is authorized to borrow in an amount up to 33 1/3% of its total assets (including the amount borrowed). The use of leverage for investment purposes creates opportunities for greater total returns, but at the same time involves risks. Any investment income or gains earned with respect to the amounts borrowed that are in excess of the interest that is due on the borrowing will augment the Fund’s income. Conversely, if the investment performance with respect to the amounts borrowed fails to cover the interest on such borrowings, the value of the Fund’s shares may decrease

10

Highland Funds I Prospectus

October 31, 2013

more quickly than would otherwise be the case. Interest payments and fees incurred in connection with such borrowings will reduce the amount of net income available for payment to Fund shareholders.

Management Risk. The Fund relies on the Adviser’s ability to achieve its investment objective. The Adviser may be incorrect in its assessment of the intrinsic value of companies whose securities the Fund holds, which may result in a decline in the value of Fund shares and failure to achieve its investment objective. The Fund’s portfolio managers use qualitative analyses and/or models. Any imperfections or limitations in such analyses and models could affect the ability of the portfolio managers to implement strategies.

Mid-Cap Company Risk. Investing in securities of mid-cap companies may entail greater risks than investments in larger, more established companies. Mid-cap companies tend to have more narrow product lines, more limited financial resources and a more limited trading market for their stocks, as compared with larger companies. As a result, their stock prices may decline significantly as market conditions change.

Non-Diversification Risk. As a non-diversified fund for the purposes of the 1940 Act, the Fund may invest a larger portion of its assets in the securities of fewer issuers than a diversified fund. The Fund’s investment in fewer issuers may result in the Fund’s shares being more sensitive to the economic results of those issuers. An investment in the Fund could fluctuate in value more than an investment in a diversified fund.

Non-U.S. Securities Risk. Investments in securities of non-U.S. issuers involve certain risks not involved in domestic investments (for example, fluctuations in foreign exchange rates (for non-U.S. securities not denominated in U.S. dollars); future foreign economic, financial, political and social developments; nationalization; exploration or confiscatory taxation; smaller markets; different trading and settlement practices; less governmental supervision; and different accounting, auditing and financial recordkeeping standards and requirements) that may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies. These risks are magnified for investments in issuers tied economically to emerging markets, the economies of which tend to be more volatile than the economies of developed markets. In addition, certain investments in non-U.S. securities may be subject to foreign withholding taxes on interest, dividends, capital gains or other income. Those taxes will reduce the Fund’s yield on any such securities. See the “Taxation” section below.

Portfolio Turnover Risk. High portfolio turnover will increase the Fund’s transaction costs and may result in increased realization of net short-term capital gains (which are taxable to shareholders as ordinary income when distributed to them), higher taxable distributions and lower after-tax performance. During the last two fiscal years, the Fund has experienced high portfolio turnover rates.

Risk of Substantial Redemptions. If substantial numbers of shares in the Fund were to be redeemed at the same time or at approximately the same time, the Fund might be required to liquidate a significant portion of its investment portfolio quickly to meet the redemptions. The Fund might be forced to sell portfolio securities at prices or at times when it would otherwise not have sold them.

Securities Lending Risk. The fund may make secured loans of its portfolio securities. Any decline in the value of a portfolio security that occurs while the security is out on loan is borne by the Fund, and will adversely affect performance. Also, there may be delays in recovery of securities loaned, losses in the investment of collateral, and loss of rights in the collateral should the borrower of the securities fail financially while holding the security.

Securities Market Risk. The value of securities owned by the Fund may go up or down, sometimes rapidly or unpredictably, due to factors affecting particular companies or the securities markets generally. A general downturn in the securities market may cause multiple asset classes to decline in value simultaneously. Many factors can affect this value and you may lose money by investing in the Fund.

Short Sales Risk. This is the risk of loss associated with any appreciation on the price of a security borrowed in connection with a short sale. The Fund may engage in short sales that are not made “against-the-box” (as defined under “Description of Principal Investments”), which means that the Fund may sell short securities even when they are not actually owned or otherwise covered at all times during the period the short position is open. Short sales that are not made “against-the-box” theoretically involve unlimited loss potential since the market price of securities sold short may continuously increase.

Small-Cap Company Risk. Investing in the securities of small-cap companies either directly or indirectly through investments in ETFs, closed-end funds or mutual funds (“Underlying Funds”) may pose greater market and liquidity risks than larger, more established companies, because of limited product lines and/or operating history, limited financial resources, limited trading markets, and the potential lack of management depth. In addition, the securities of such companies are typically more volatile than securities of larger capitalization companies.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the FDIC or any other government agency. As with any mutual fund, there is no guarantee that the Fund will achieve its goal.

Risk/Return Bar Chart and Table

The bar chart and the performance table below provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund’s Class A Shares from year to year and by showing how the Fund’s average annual returns for the Fund’s Class A, Class C and Class Z Shares compared to those of a broad measure of market performance. As with all mutual funds, the Fund’s past performance (before and after taxes) does not predict how the Fund will perform in the future. Both the chart and the table assume the reinvestment of dividends and distributions. The bar chart does not reflect the deduction of applicable sales charges for Class A Shares. If sales charges had been reflected, the returns for Class A Shares would be less than those shown below. Updated information on the Fund’s performance can be

11

obtained by visiting https://www.highlandfunds.com/Funds———Performance/Mutual-Funds/Alternative-Investment/Long-Short-Equity or by calling 1-877-665-1287.

Annual Total Return ¹

(As of December 31 for Class A Shares)

The highest calendar quarter total return for Class A Shares of the Fund was 10.42% for the quarter ended September 30, 2009 and the lowest calendar quarter total return was (5.59)% for the quarter ended September 30, 2008.

Principal Risks

When you sell Fund shares, they may be worth less than what you paid for them. Consequently, you can lose money by

14

Highland Funds I Prospectus

October 31, 2013

investing in the Fund. No assurance can be given that the Fund will achieve its objective, and investment results may vary substantially over time and from period to period. An investment in the Fund is not appropriate for all investors.

Counterparty Risk. A counterparty (the other party to a transaction or an agreement or the party with whom the Fund executes transactions) to a transaction with the Fund may be unable or unwilling to make timely principal, interest or settlement payments, or otherwise honor its obligations.

Credit Risk. The issuers of certain securities or the counterparties of a derivatives contract or repurchase contract might be unable or unwilling (or perceived as being unable or unwilling) to make interest and/or principal payments when due, or to otherwise honor its obligations. Debt securities are subject to the risk of non-payment of scheduled interest and/or principal. Non-payment would result in a reduction of income to the Fund, a reduction in the value of the obligation experiencing non-payment and a potential decrease in the Net Asset Value (“NAV”) of the Fund.

Currency Risk. Fluctuations in exchange rates will adversely affect the value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

Debt Securities Risk. The value of debt securities typically changes in response to various factors, including, by way of example, market-related factors (such as changes in interest rates or changes in the risk appetite of investors generally) and changes in the actual or perceived ability of the issuer (or of issuers generally) to meet its (or their) obligations. During periods of rising interest rates, debt securities generally decline in value. Conversely, during periods of falling interest rates, debt securities generally rise in value. This kind of market risk is generally greater for Funds investing in debt securities with longer maturities.

Derivatives Risk. Derivatives Risk is a combination of several risks, including the risks that: (1) an investment in a derivative instrument may not correlate well with the performance of the securities or asset class to which the Fund seeks exposure, (2) derivative contracts, including options, may expire worthless and the use of derivatives may result in losses to the Fund, (3) a derivative instrument entailing leverage may result in a loss greater than the principal amount invested, (4) derivatives not traded on an exchange may be subject to credit risk, for example, if the counterparty does not meet its obligations (see also “Counterparty Risk”), and (5) derivatives not traded on an exchange may be subject to liquidity risk and the related risk that the instrument is difficult or impossible to value accurately. As a general matter, when a Fund establishes certain derivative instrument positions, such as certain futures, options and forward contract positions, it will segregate liquid assets (such as cash, U.S. Treasury bonds or commercial paper) equivalent to the Fund’s outstanding obligations under the contract or in connection with the position. In addition, recent legislation has called for a new regulatory framework for the derivatives market. The impact of the new regulations are still unknown, but has the potential to increase the costs of using derivatives, may limit the availability of some forms of derivatives or the Fund’s ability to use derivatives, and may adversely affect the performance of some derivative instruments used by the Fund as well as the Fund’s ability to pursue its investment objective through the use of such instruments.

Emerging Markets Risk. Investing in securities of issuers tied economically to emerging markets entails all of the risks of investing in securities of non-U.S. issuers detailed below under “Non-U.S. Securities Risk” to a heightened degree. These heightened risks include: (i) greater risks of expropriation, confiscatory taxation, nationalization, and less social, political and economic stability; (ii) the smaller size of the markets for such securities and a lower volume of trading, resulting in lack of liquidity and in price volatility; (iii) greater fluctuations in currency exchange rates; and (iv) certain national policies that may restrict a Fund’s investment opportunities, including restrictions on investing in issuers or industries deemed sensitive to relevant national interests.

Equity Securities Risk. Because it purchases common stocks and other equity securities, the Fund is subject to the risk that stock prices will fall over short or long periods of time. In addition, common stocks represent a share of ownership in a company, and rank after bonds and preferred stock in their claim on the company’s assets in the event of bankruptcy.

ETF Risk. The price movement of an ETF may not exactly track the underlying index and may result in a loss. In addition, shareholders bear both their proportionate share of the Fund’s expenses and similar expenses of the underlying investment company when the Fund invests in shares of another investment company.

Hedging Risk. Although intended to limit or reduce investment risk, hedging strategies may also limit or reduce the potential for profit. There is no assurance that hedging strategies will be successful.

Illiquid and Restricted Securities Risk. The Sub-Adviser may not be able to sell illiquid or restricted securities at the price it would like or may have to sell them at a loss. Securities of non-U.S. issuers and emerging markets securities in particular, are subject to greater liquidity risk.

Industry Concentration Risk. Because the Fund normally invests at least 80% of the value of its assets in healthcare companies, the Fund’s performance largely depends on the overall condition of the healthcare industry and the Fund is susceptible to economic, political and regulatory risks or other occurrences associated with the healthcare industry.

Interest Rate Risk. When interest rates decline, the value of fixed rate securities already held by the Fund can be expected to rise. Conversely, when interest rates rise, the value of existing fixed rate portfolio securities can be expected to decline. A fund with a longer average portfolio duration will be more sensitive to changes in interest rates than a fund with a shorter average portfolio duration.

Leverage Risk. The Fund is authorized to borrow in an amount up to 33 1/3% of its total assets (including the amount borrowed). The use of leverage for investment purposes creates opportunities for greater total returns, but at the same time involves risks. Any investment income or gains earned with respect to the amounts borrowed that are in excess of the interest that is due on the borrowing will augment the Fund’s income. Conversely, if the investment performance with

15

respect to the amounts borrowed fails to cover the interest on such borrowings, the value of the Fund’s shares may decrease more quickly than would otherwise be the case. Interest payments and fees incurred in connection with such borrowings will reduce the amount of net income available for payment to Fund shareholders.

Management Risk. The Fund relies on the Sub-Adviser’s ability to achieve its investment objective. The Sub-Adviser may be incorrect in its assessment of the intrinsic value of companies whose securities the Fund holds, which may result in a decline in the value of Fund shares and failure to achieve its investment objective. The Fund’s portfolio managers use qualitative analyses and/or models. Any imperfections or limitations in such analyses and models could affect the ability of the portfolio managers to implement strategies.

Mid-Cap Company Risk. Investing in securities of mid-cap companies may entail greater risks than investments in larger, more established companies. Mid-cap companies tend to have more narrow product lines, more limited financial resources and a more limited trading market for their stocks, as compared with larger companies. As a result, their stock prices may decline significantly as market conditions change.

Non-Diversification Risk. As a non-diversified fund for the purposes of the 1940 Act, the Fund may invest a larger portion of its assets in the securities of fewer issuers than a diversified fund. The Fund’s investment in fewer issuers may result in the Fund’s shares being more sensitive to the economic results of those issuers. An investment in the Fund could fluctuate in value more than an investment in a diversified fund. This risk is particularly pronounced for the Fund, which from time to time may own a very small number of positions, each of which is a relatively large portion of the Fund’s portfolio.

Non-U.S. Securities Risk. Investments in securities of non-U.S. issuers involve certain risks not involved in domestic investments (for example, fluctuations in foreign exchange rates (for non-U.S. securities not denominated in U.S. dollars); future foreign economic, financial, political and social developments; nationalization; exploration or confiscatory taxation; smaller markets; different trading and settlement practices; less governmental supervision; and different accounting, auditing and financial recordkeeping standards and requirements) that may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies. These risks are magnified for investments in issuers tied economically to emerging markets, the economies of which tend to be more volatile than the economies of developed markets. In addition, certain investments in non-U.S. securities may be subject to foreign withholding taxes on interest, dividends, capital gains or other income. Those taxes will reduce the Fund’s yield on any such securities. See the “Taxation” section below.

Portfolio Turnover Risk. High portfolio turnover will increase the Fund’s transaction costs and may result in increased realization of net short-term capital gains (which are taxable to shareholders as ordinary income when distributed to them), higher taxable distributions and lower after-tax performance. During the last fiscal year, the Fund experienced a high portfolio turnover rate.

Risk of Substantial Redemptions. If substantial numbers of shares in the Fund were to be redeemed at the same time or at approximately the same time, the Fund might be required to liquidate a significant portion of its investment portfolio quickly to meet the redemptions. The Fund might be forced to sell portfolio securities at prices or at times when it would otherwise not have sold them.

Securities Lending Risk. The fund may make secured loans of its portfolio securities. Any decline in the value of a portfolio security that occurs while the security is out on loan is borne by the Fund, and will adversely affect performance. Also, there may be delays in recovery of securities loaned, losses in the investment of collateral, and loss of rights in the collateral should the borrower of the securities fail financially while holding the security.

Securities Market Risk. The value of securities owned by the Fund may go up or down, sometimes rapidly or unpredictably, due to factors affecting particular companies or the securities markets generally. A general downturn in the securities market may cause multiple asset classes to decline in value simultaneously. Many factors can affect this value and you may lose money by investing in the Fund.

Short Sales Risk. This is the risk of loss associated with any appreciation on the price of a security borrowed in connection with a short sale. The Fund may engage in short sales that are not made “against-the-box” (as defined under “Description of Principal Investments”), which means that the Fund may sell short securities even when they are not actually owned or otherwise covered at all times during the period the short position is open. Short sales that are not made “against-the-box” theoretically involve unlimited loss potential since the market price of securities sold short may continuously increase.

Small-Cap Company Risk. Investing in the securities of small-cap companies either directly or indirectly through investments in ETFs, closed-end funds or mutual funds (“Underlying Funds”) may pose greater market and liquidity risks than larger, more established companies, because of limited product lines and/or operating history, limited financial resources, limited trading markets, and the potential lack of management depth. In addition, the securities of such companies are typically more volatile than securities of larger capitalization companies.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the FDIC or any other government agency. As with any mutual fund, there is no guarantee that the Fund will achieve its goal.

Risk/Return Bar Chart and Table

The bar chart and the performance table below provide an indication of the risks of investing in the Fund by showing changes in the performance of the Fund’s Class A Shares for the most recent calendar year and by showing how the Fund’s average annual returns for the Fund’s Class A, Class C and Class Z Shares compared to those of a broad measure of market performance. As with all mutual funds, the Fund’s past performance (before and after taxes) does not predict how the Fund will perform in the future. Both the chart and the table

16

Highland Funds I Prospectus

October 31, 2013

assume the reinvestment of dividends and distributions. The table reflects the deduction of applicable sales charges for Class A and Class C Shares. The bar chart does not reflect the deduction of applicable sales charges for Class A Shares. If sales charges had been reflected, the returns for Class A Shares would be less than those shown below. Updated information on the Fund’s performance can be obtained by visiting https://www.highlandfunds.com/Funds———Performance/Mutual-Funds/Alternative-Investment/Long-Short-Healthcare or by calling 1-877-665-1287.

Annual Total Return ¹

(As of December 31 for Class A Shares)

The highest calendar quarter total return for Class A Shares of the Fund was 16.25% for the quarter ended December 31, 2009 and the lowest calendar quarter total return was (11.78)% for the quarter ended March 31, 2009.

Description of Principal Risks

securities may be repaid more slowly than expected. As a result, the maturity of the debt instrument is extended, increasing the potential for loss.

The value of a debt security also depends on the issuer’s credit quality or ability to pay principal and interest when due. The value of a debt security is likely to fall if an issuer or the guarantor of a security is unable or unwilling (or perceived to be unable or unwilling) to make timely principal and/or interest payments or otherwise to honor its obligations, or if the debt security’s rating is downgraded by a credit rating agency. The obligations of issuers (and obligors of asset-backed securities) are subject to bankruptcy, insolvency, and other laws affecting the rights and remedies of creditors. The value of a debt security can also decline in response to other changes in market, economic, industry, political, and regulatory conditions that affect a particular type of debt security or issuer or debt securities generally. The values of many debt securities may fall in response to a general increase in investor risk aversion or a decline in the confidence of investors generally in the ability of issuers to meet their obligations.

Leveraged Loans are subject to the same risks typically associated with debt securities. In addition, Leveraged Loans, which typically hold a senior position in the capital structure of a borrower, are subject to the risk that a court could subordinate such loans to presently existing or future indebtedness or take other action detrimental to the holders of Leveraged Loans. Leveraged Loans are also especially subject to the risk that the value of the collateral, if any, securing a loan may decline, be insufficient to meet the obligations of the borrower, or be difficult to liquidate.

Derivatives Risk.  All of the Funds may invest in derivatives, which are financial contracts whose value depends on, or is derived from, the value of underlying assets, reference rates, or indices. Derivatives involve the risk that changes in their value may not move as expected relative to the value of the assets, rates, or indices they are designed to track. Derivatives include futures, non-U.S. currency contracts, swap contracts, warrants, and opinions contracts. Derivatives may relate to securities, interest rates, currencies or currency exchange rates, inflation rates, commodities, and indices.

There are several risks associated with derivatives transactions. The use of derivatives involves risks that are in addition to, and potentially greater than, the risks of investing directly in securities and other more traditional assets. A decision as to whether, when and how to use derivatives involves the exercise of skill and judgment, and even a well conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. The use of derivative transactions may result in losses greater than if they had not been used, may require a Fund to sell or purchase portfolio securities at inopportune times or for prices other than current market values, may limit the amount of appreciation the Fund can realize on an investment or may cause the Fund to hold a security that it might otherwise sell. A Fund may enter into credit derivatives, such as credit default swaps and credit default index investments, including loan credit default swaps and loan credit default index swaps. The use by a Fund of credit default swaps may have the effect of creating a short position in a security. These investments can create investment leverage and may create additional investment risks that may subject a Fund to greater volatility than investments in more traditional securities. Derivative contracts may expire worthless.

A Fund may invest in derivatives with a limited number of counterparties, and events affecting the creditworthiness of any of those counterparties may have a pronounced effect on the Fund. Derivatives risk is particularly acute in environments (like those of 2008) in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers and subsequent market disruptions. In addition, during those periods, a Fund may have a greater need for cash to provide collateral for large swings in its mark-to-market obligations under the derivatives in which it has invested.

A Fund’s use of derivatives may not be effective or have the desired results. Moreover, suitable derivatives will not be available in all circumstances. For example, the economic costs of taking some derivative positions may be prohibitive, and if a counterparty or its affiliate is deemed to be an affiliate of a Fund, the Funds will not be permitted to trade with that counterparty. In addition, the Adviser may decide not to use derivatives to hedge or otherwise reduce a Fund’s risk exposures, potentially resulting in losses for the Fund.

Swap contracts and other OTC derivatives are highly susceptible to liquidity risk (see “Liquidity Risk”) and counterparty risk (see “Counterparty Risk”), and are subject to documentation risks. Because many derivatives have a leverage component (i.e., a notional value in excess of the assets needed to establish and/or maintain the derivative position), adverse changes in the value or level of the underlying asset, rate or index may result in a loss substantially greater than the amount invested in the derivative itself. See “Leverage Risk” below.

Derivatives also present other risks described in this section, including market risk, liquidity risk, currency risk, credit risk, and counterparty risk. Special tax considerations apply to the Funds’ use of derivatives. See the “Taxation” section below.

Under recently adopted rules and regulations, transactions in some types of swaps (including interest rate swaps and credit default swaps on North American and European indices) are required to be centrally cleared. In a transaction involving those swaps (“cleared derivatives”), a Fund’s counterparty is a clearing house, rather than a bank or broker. Since the Funds are not members of clearing houses and only members of a clearing house (“clearing members”) can participate directly in the clearing house, the Funds will hold cleared derivatives through accounts at clearing members. In cleared derivatives transactions, the Funds will make payments (including margin payments) to and receive payments from a clearing house through their accounts at clearing members. Clearing members guarantee performance of their clients’ obligations to the clearing house.

26

Highland Funds I Prospectus

October 31, 2013

In many ways, cleared derivative arrangements are less favorable to mutual funds than bilateral arrangements. For example, the Funds may be required to provide more margin for cleared derivatives transactions than for bilateral derivatives transactions. Also, in contrast to a bilateral derivatives transaction, following a period of notice to a Fund, a clearing member generally can require termination of an existing cleared derivatives transaction at any time or an increase in margin requirements above the margin that the clearing member required at the beginning of a transaction. Clearing houses also have broad rights to increase margin requirements for existing transactions or to terminate those transactions at any time. Any increase in margin requirements or termination of existing cleared derivatives transactions by the clearing member or the clearing house could interfere with the ability of a Fund to pursue its investment strategy. Further, any increase in margin requirements by a clearing member could expose a Fund to greater credit risk to its clearing member, because (as described under “Counterparty Risk”) margin for cleared derivatives transactions in excess of a clearing house’s margin requirements typically is held by the clearing member. Also, a Fund is subject to risk if it enters into a derivatives transaction that is required to be cleared (or that the Adviser expects to be cleared), and no clearing member is willing or able to clear the transaction on the Fund’s behalf. In those cases, the transaction might have to be terminated, and the Fund could lose some or all of the benefit of the transaction, including loss of an increase in the value of the transaction and/or loss of hedging protection. In addition, the documentation governing the relationship between the Funds and clearing members is drafted by the clearing members and generally is less favorable to the Funds than typical bilateral derivatives documentation. For example, documentation relating to cleared derivatives generally includes a one-way indemnity by the Funds in favor of the clearing member for losses the clearing member incurs as the Funds’ clearing member and typically does not provide the Funds any remedies if the clearing member defaults or becomes insolvent.

These and other new rules and regulations could, among other things, further restrict a Fund’s ability to engage in, or increase the cost to the Fund of, derivatives transactions, for example, by making some types of derivatives no longer available to the Fund, increasing margin or capital requirements, or otherwise limiting liquidity or increasing transaction costs. These regulations are new and evolving, so their potential impact on the Funds and the financial system are not yet known. While the new regulations and central clearing of some derivatives transactions are designed to reduce systemic risk (i.e., the risk that the interdependence of large derivatives dealers could cause them to suffer liquidity, solvency or other challenges simultaneously), there is no assurance that the new clearing mechanisms will achieve that result, and in the meantime, as noted above, central clearing exposes the Funds to new kinds of risks and costs.

Equity Securities Risk. The market prices of equity securities owned by a Fund may go up or down, sometimes rapidly or unpredictably. The value of a security may decline for a number of reasons that may directly relate to the issuer, such as management performance, fundamental changes to the business, financial leverage, non-compliance with regulatory requirements and reduced demand for the issuer’s goods or services. The values of equity securities also may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Certain equity securities may decline in value even during periods when the prices of equity securities in general are rising, or may not perform as well as the market in general. In addition to these risks, preferred stock and convertible securities are also subject to the risk that issuers will not make payments on securities held by a Fund, which could result in losses to the Fund. The credit quality of preferred stock and convertible securities held by a Fund may be lowered if an issuer’s financial condition changes, leading to greater volatility in the price of the security. In addition, a company’s preferred stock generally pays dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred stock will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. The market value of convertible securities also tends to fall when prevailing interest rates rise.

ETF Risk. The value of ETFs can be expected to increase and decrease in value in proportion to increases and decreases in the indices that they are designed to track. The volatility of different index tracking stocks can be expected to vary in proportion to the volatility of the particular index they track. ETFs are traded similarly to stocks of individual companies. Although an ETF is designed to provide investment performance corresponding to its index, it may not be able to exactly replicate the performance of its index because of its operating expenses and other factors.

Focused Investment Risk . Funds whose investments are focused in particular countries, regions, sectors, companies, or industries with high positive correlations to one another (e.g., different industries within broad sectors, such as technology or financial services), or in securities from issuers with high positive correlations to one another, are subject to greater overall risk than funds whose investments are more diversified. A Fund that focuses its investments in a particular type of security or sector, or in securities of companies in a particular industry, is vulnerable to events affecting those securities, sectors, or companies. Securities, sectors, or companies that share common characteristics are often subject to similar business risks and regulatory burdens, and often react similarly to specific economic, market, political or other developments.

Floating Rate Opportunities Fund’s investments in Senior Loans arranged through private negotiations between a Borrower and several financial institutions may expose the Fund to risks associated with the financial services industry. Financial services companies are subject to extensive government regulation, which can limit both the amounts and types of loans and other financial commitments they can make and

27

Description of Principal Risks

the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds and can fluctuate significantly when interest rates change. Because financial services companies are highly dependent on short-term interest rates, they can be adversely affected by downturns in the U.S. and foreign economies or changes in banking regulations. Credit losses resulting from financial difficulties of borrowers can negatively affect financial services companies. Insurance companies can be subject to severe price competition. The financial services industry is currently undergoing relatively rapid change as existing distinctions between financial service segments become less clear. For instance, recent business combinations have included insurance, finance, and securities brokerage under single ownership. Some primarily retail corporations have expanded into the securities and insurance industries. Moreover, the federal laws generally separating commercial and investment banking have been repealed. These changes may make it more difficult for the Adviser to analyze loans in this industry. Additionally, the recently increased volatility in the financial markets and implementation of the recent financial reform legislation may affect the financial services industry as a whole in ways that may be difficult to predict.

Hedging Risk. There are several risks in connection with the use by a Fund of futures contracts and related options as a hedging device. One risk arises because of the imperfect correlation between movements in the prices of the futures contracts and options and movements in the underlying securities or index or movements in the prices of a Fund’s securities which are the subject of a hedge. The Adviser or Sub-Adviser, as applicable, will, however, attempt to reduce this risk by purchasing and selling, to the extent possible, futures contracts and related options on securities and indexes the movements of which will, in its judgment, correlate closely with movements in the prices of the underlying securities or index and the Fund’s portfolio securities sought to be hedged. Successful use of futures contracts and options by a Fund for hedging purposes is also subject to the Adviser’s or Sub-Adviser’s, as applicable, ability to predict correctly movements in the direction of the market. It is possible that, where a Fund has purchased puts on futures contracts to hedge its portfolio against a decline in the market, the securities or index on which the puts are purchased may increase in value and the value of securities held in the portfolio may decline. If this occurred, the Fund would lose money on the puts and also experience a decline in the value of its portfolio securities. In addition, the prices of futures, for a number of reasons, may not correlate perfectly with movements in the underlying securities or index due to certain market distortions. First, all participants in the futures market are subject to margin deposit requirements. Such requirements may cause investors to close futures contracts through offsetting transactions which could distort the normal relationship between the underlying security or index and futures markets. Second, the margin requirements in the futures markets are less onerous than margin requirements in the securities markets in general, and as a result the futures markets may attract more speculators than the securities markets do. Increased participation by speculators in the futures markets may also cause temporary price distortions. Due to the possibility of price distortion, even a correct forecast of general market trends by the Adviser or Sub-Adviser, as applicable, still may not result in a successful hedging transaction over a very short time period. In addition, to maintain margin requirements, a Fund may have to sell portfolio securities at disadvantageous prices or times because it may not be possible to liquidate a position at a reasonable price. The earmarking of such assets also will have the effect of limiting a Fund’s ability otherwise to invest those assets. Special tax considerations apply to the Fund’s hedging transactions. See the “Taxation” section below.

High-Yield Debt Securities Risk. Each Fund may invest in below investment grade securities (also known as “high-yield securities” or “junk bonds”). Below investment grade securities may be fixed or variable rate obligations and are rated below investment grade (Ba/BB or lower) by a nationally recognized statistical rating organization or are unrated but deemed by the Adviser or Sub-Adviser, as applicable, to be of comparable quality. Such securities should be considered speculative with respect to capacity to pay interest and repay principal in accordance with the terms of the obligation. High-yield debt securities are frequently issued by corporations in the growth stage of their development, but also may be issued by established companies.

Below investment grade securities have greater credit and liquidity risk than more highly rated obligations and are generally unsecured and may be subordinate to other obligations of the obligor. The lower rating of high-yield securities reflects a greater possibility that adverse changes in the financial condition of the issuer or in general economic conditions (including, for example, a substantial period of rising interest rates or declining earnings) or both may impair the ability of the issuer to make payment of principal and interest. Many issuers of high-yield securities are highly leveraged and their relatively high debt to equity ratios create increased risks that their operations might not generate sufficient cash flow to service their obligations. Overall declines in the below investment grade bond market and other markets may adversely affect such issuers by inhibiting their ability to refinance their obligations at maturity. Investments in obligations of issuers that are generally trading at significantly higher yields than had been historically typical of the applicable issuer’s obligations may include debt obligations that have a heightened probability of being in covenant or payment default in the future. Such investments generally are considered speculative. The repayment of defaulted obligations is subject to significant uncertainties. Defaulted obligations might be repaid only after lengthy workout or bankruptcy proceedings, during which the issuer might not make any interest or other payments. Typically such workout or bankruptcy proceedings result in only partial recovery of cash payments or an exchange of the defaulted security for other debt or equity securities of the issuer or its affiliates, which may in turn be illiquid or speculative. High-yield securities will be subject to certain additional risks to the extent that such obligations may be unsecured and subordinated to substantial amounts of senior indebtedness, all or a significant portion of

28

Highland Funds I Prospectus

October 31, 2013

which may be secured. Moreover, such obligations may not be protected by financial covenants or limitations upon additional indebtedness and are unlikely to be secured by collateral. See “Income Tax Considerations” in the SAI for a discussion of special tax consequences associated with below investment grade securities owned by Floating Rate Opportunities Fund. There is no limit on the percentage of assets that Floating Rate Opportunities Fund may invest in Senior Loans and other securities that are rated below investment grade or that are unrated but of comparable quality.

Illiquid and Restricted Securities Risk. Illiquid investments may be difficult to resell at approximately the price they are valued in the ordinary course of business within seven days. When investments cannot be sold readily at the desired time or price, a Fund may have to accept a much lower price, may not be able to sell the investment at all or may be forced to forego other investment opportunities, all of which may adversely impact the Fund’s returns. Illiquid investments also may be subject to valuation risk. Restricted securities (including Rule 144A securities) may be subject to legal restraints on resale and, therefore, are typically less liquid than other securities. The prices received from selling restricted securities in privately negotiated transactions may be less than those originally paid by a Fund. Investors in restricted securities may not benefit from the same investor protections as publicly traded securities.

Industry Concentration Risk. The performance of a Fund that may invest a significant portion of its assets in a particular sector or industry may be closely tied to the performance of companies in a limited number of sectors or industries. Companies in a single sector often share common characteristics, are faced with the same obstacles, issues and regulatory burdens and their securities may react similarly to adverse market conditions. To the extent that a Fund concentrates its investment in particular issuers, countries, geographic regions, industries or sectors, the Fund may be subject to greater risks of adverse developments in such areas of focus than a fund that invests in a wider variety of issuers, countries, geographic regions, industries, sectors or investments. The price movements of investments in a particular sector or industry may be more volatile than the price movements of more broadly diversified investments. Long/Short Equity Fund and Floating Rate Opportunities Fund may invest up to (but not including) 25% of its total assets in the securities of companies in one industry. Long/Short Healthcare Fund invests at least 80% of its total assets in healthcare companies.

Because of Long/Short Healthcare Fund’s policy of investing primarily in securities issued by healthcare companies, the Fund is susceptible to economic, political or regulatory risks or other occurrences associated with the healthcare industry. The Fund faces the risk that economic prospects of healthcare companies may fluctuate dramatically because of changes in the regulatory and competitive environments. See “Regulatory Risk” below. A significant portion of healthcare services are funded or subsidized by the government, which means that changes in government policies, at the state or federal level, may affect the demand for healthcare products and services. Other risks include the possibility that regulatory approvals (which often entail lengthy application and testing procedures) will not be granted for new drugs and medical products, the chance of lawsuits against healthcare companies related to product liability issues, and the rapid speed at which many healthcare products and services become obsolete.

Interest Rate Risk. When interest rates decline, the value of fixed rate securities already held by a Fund can be expected to rise. Conversely, when interest rates rise, the value of existing fixed-rate portfolio securities can be expected to decline. However, Floating Rate Opportunities Fund will primarily invest in floating rate obligations, including Senior Loans, the rates on which periodically adjust with changes in market interest rates. Consequently, the Fund’s exposure to fluctuations in interest rates will generally be limited until the time that the interest rates on the Senior Loans in its portfolio are reset, but the Fund will be exposed at all times to fluctuations in interest rates with respect to the fixed rate investments in its portfolio, if any. Because market interest rates are currently near their lowest levels in many years, there is a greater than normal risk that the fixed rate investments in the Fund’s portfolio will decline in value due to rising interest rates. Each of Long/Short Equity Fund and Long/Short Healthcare Fund have no policy limiting the maturities of their investments. To the extent each of these Funds invests in fixed-rate debt securities with longer maturities, the Funds are subject to greater interest rate risk than funds investing solely in shorter-term fixed-rate debt securities. In addition, in a period of rising interest rates, the higher cost of any leverage employed by a Fund and/or increasing defaults by issuers of high-yield securities would likely exacerbate any decline in the Fund’s NAV. If an issuer of a debt security containing a redemption or call provision exercises either provision in a declining interest rate market, the Fund would likely replace the security with a security having a lower interest rate, which could result in a decreased return for shareholders.

To the extent that changes in market rates of interest are reflected not in a change to a base rate (such as LIBOR) but in a change in the spread over the base rate, which is payable on loans of the type and quality in which Floating Rate Opportunities Fund invests, the Fund’s NAV could be adversely affected. This is because the value of a Senior Loan is partially a function of whether the Senior Loan is paying what the market perceives to be a market rate of interest, given its individual credit and other characteristics. However, unlike changes in market rates of interest for which there is generally only a temporary lag before the portfolio reflects those changes, changes in a Senior Loan’s value based on changes in the market spread on Senior Loans in the Fund’s portfolio may be of longer duration.

Leverage Risk. When deemed appropriate by the Adviser, Sub-Adviser or portfolio manager(s), as applicable, and subject to applicable regulations, each Fund may use leverage in its investment program, including the use of borrowed funds and investments in certain types of options, such as puts, calls and warrants, which may be purchased for a fraction of the price

29

Description of Principal Risks

of the underlying securities while giving the purchaser the full benefit of movement in the market of those underlying securities. While such strategies and techniques increase the opportunity to achieve higher returns on the amounts invested, they also increase the risk of loss. To the extent a Fund purchases securities with borrowed funds, its net assets will tend to increase or decrease at a greater rate than if borrowed funds are not used. The level of interest rates generally, and the rates at which such funds may be borrowed in particular, could affect the operating results of a Fund. If the interest expense on borrowings were to exceed the net return on the portfolio securities purchased with borrowed funds, a Fund’s use of leverage would result in a lower rate of return than if the Fund were not leveraged.

If the amount of borrowings that a Fund may have outstanding at any one time is large in relation to its capital, fluctuations in the market value of the Fund’s portfolio will have disproportionately large effects in relation to the Fund’s capital and the possibilities for profit and the risk of loss will therefore be increased. Any investment gains made with the additional monies borrowed will generally cause the NAV of the Fund to rise more rapidly than would otherwise be the case. Conversely, if the investment performance of the investments acquired with borrowed money fails to cover their cost to the Fund, the NAV of the Fund will generally decline faster than would otherwise be the case. If the Fund employs leverage, the Adviser or Sub-Adviser, as applicable, will benefit because the Fund’s Average Daily Managed Assets will increase with leverage and the Adviser or Sub-Adviser, as applicable, is compensated based on a percentage of Average Daily Managed Assets.

Under the terms of any credit facility, a Fund may be required to, among other things, pledge some or all of its assets, limit its ability to pay distributions in certain circumstances, incur additional debts and engage in certain transactions. Such agreements could limit a Fund’s ability to pursue its investment strategies. The terms of any credit facility may be more restrictive than those described.

Limited Information Risk. The types of Senior Loans in which Floating Rate Opportunities Fund will invest may not have been rated by a NRSRO, have not been registered with the SEC or any state securities commission, and have not been listed on any national securities exchange. Although the Fund will generally have access to financial and other information made available to the Lenders in connection with Senior Loans, the amount of public information available with respect to Senior Loans will generally be less extensive than that available for rated, registered or exchange listed securities. As a result, the performance of the Fund and its ability to meet its investment objective is more dependent on the analytical ability of the Adviser than would be the case for an investment company that invests primarily in rated, registered or exchange-listed securities.

Liquidity Risk. Liquidity risk is the risk that low trading volume, lack of a market maker, large position size, or legal restrictions (including daily price fluctuation limits or “circuit breakers”) limits or prevents a Fund from selling particular securities or unwinding derivative positions at desirable prices. A Fund is also exposed to liquidity risk when it has an obligation to purchase particular securities (e.g., as a result of entering into reverse repurchase agreements, writing a put, or closing a short position). When there is no willing buyer or investments cannot be readily sold or closed out, a Fund may have to sell at a lower price than the price at which a Fund is carrying the investments or may not be able to sell the investments at all, each of which would have a negative effect on a Fund’s performance. Although most of a Fund’s investments must be liquid at the time of investment, investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil.

Management Risk. Each Fund is subject to management risk because it relies on the Adviser’s or Sub-Adviser’s, as applicable, ability to achieve its investment objective. Each Fund runs the risk that the Adviser’s or Sub-Adviser’s, as applicable, investment techniques will fail to produce desired results and cause the Fund to incur significant losses. The Adviser or Sub-Adviser, as applicable, also may fail to use derivatives effectively, choosing to hedge or not to hedge positions at disadvantageous times. In addition, if one or more key individuals leave, the Adviser or Sub-Adviser, as applicable, may not be able to hire qualified replacements or may require an extended time to do so. This situation could prevent a Fund from achieving its investment objectives. Funds’ portfolio managers use quantitative analyses and/or models. Any imperfections or limitations in such analyses and models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security.

Non-Diversification Risk. Due to the nature of each Fund’s investment strategy and its non-diversified status (for purposes of the 1940 Act), each Fund may invest a greater percentage of its assets in the securities of fewer issuers than a “diversified” fund, and accordingly may be more vulnerable to changes in the value of those issuers’ securities. A Fund that invests in the securities of a limited number of issuers is particularly exposed to adverse developments affecting those issuers, and a decline in the market value of a particular security held by the Fund is likely to affect the Fund’s performance more than if the Fund invested in the securities of a larger number of issuers.

Non-Payment Risk. Debt securities are subject to the risk of non-payment of scheduled interest and/or principal. Non-payment would result in a reduction of income to the Fund, a reduction in the value of the security experiencing non-payment and a potential decrease in the NAV of a Fund. There can be no assurance that the liquidation of any collateral would satisfy the Borrower’s obligation in the event of non-payment of scheduled interest or principal payments, or that such collateral could be readily liquidated. Moreover, as a

30

Highland Funds I Prospectus

October 31, 2013

practical matter, most Borrowers cannot satisfy their debts by selling their assets. Borrowers pay their debts from the cash flow they generate. This is particularly the case for Borrowers that are highly leveraged. Many of the debt securities purchased by Floating Rate Opportunities Fund will be to highly leveraged Borrowers. If the Borrower’s cash flow is insufficient to pay its debts as they come due, the Borrower is far more likely to seek to restructure its debts than it is to sell off assets to pay its Senior Loans. Borrowers may try to restructure their debts either by seeking protection from creditors under Chapter 11 of the U.S. Bankruptcy Code (the “Bankruptcy Code”) or negotiating a work out. In the event of bankruptcy of a Borrower, the Fund could experience delays or limitations with respect to its ability to realize the benefits of the collateral securing a debt security. The Agent generally is responsible for determining that the Lenders have obtained a perfected security interest in the collateral securing the debt security. If a Borrower files for protection from creditors under Chapter 11 of the Bankruptcy Code, the Bankruptcy Code will impose an automatic stay that prohibits the Agent from liquidating collateral. The Agent may ask the bankruptcy court to lift the stay. As a practical matter, the court is unlikely to lift the stay if it concludes that the Borrower has a chance to emerge from the reorganization proceedings and the collateral is likely to hold most of its value. If the Lenders have a perfected security interest, the debt security will be treated as a separate class in the reorganization proceedings and will retain a priority interest in the collateral. Chapter 11 reorganization plans typically are the product of negotiation among the Borrower and the various creditor classes. Successful negotiations may require the Lenders to extend the time for repayment, change the interest rate or accept some consideration in the form of junior debt or equity securities. A work out outside of bankruptcy may produce similar concessions by senior lenders.

Non-U.S. Securities and Emerging Markets Risk. Investing in non-U.S. securities involves additional and more varied risks than investing in U.S. investments, including, but not limited to: fluctuations in foreign exchange rates (for non-U.S. securities not denominated in U.S. dollars); future foreign economic, financial, political and social developments; different legal systems; the possible imposition of exchange controls or other foreign governmental laws or restrictions; lower trading volume; much greater price volatility and illiquidity of certain non-U.S. securities markets; different trading and settlement practices; less governmental supervision; changes in currency exchange rates; high and volatile rates of inflation; fluctuating interest rates; less publicly available information; and different accounting, auditing and financial recordkeeping standards and requirements.

Because non-U.S. issuers are not generally subject to uniform accounting, auditing and financial reporting standards and practices comparable to those applicable to U.S. issuers, there may be less publicly available information about certain non-U.S. issuers than about U.S. issuers. Evidence of securities ownership may be uncertain in many foreign countries. Securities of non-U.S. issuers are generally less liquid than securities of comparable U.S. issuers. In certain countries, there is less government supervision and regulation of stock exchanges, brokers and listed companies than in the U.S. In addition, with respect to certain foreign countries, especially emerging market countries, there is the possibility of expropriation or confiscatory taxation, political or social instability, war, terrorism, nationalization, limitations on the removal of funds or other assets or diplomatic developments which could affect U.S. investments in those countries. Commissions (and other transaction costs) for non-U.S. securities are generally higher than those on U.S. securities. In addition, it is expected that the expenses for custodian arrangements of a Fund’s non-U.S. securities will be somewhat greater than the expenses for a fund that invests primarily in domestic securities. Certain investments in non-U.S. securities may also be subject to foreign withholding taxes on interest, dividends, capital gains or other income. Those taxes will reduce a Fund’s yield on any such securities.

The value of the non-U.S. securities held by a Fund that are not U.S. dollar-denominated may be significantly affected by changes in currency exchange rates. The U.S. dollar value of a foreign denominated non-U.S. security generally decreases when the value of the U.S. dollar rises against the foreign currency in which the security is denominated and tends to increase when the value of the U.S. dollar falls against such currency. Currencies of certain countries may be volatile and therefore may affect the value of securities denominated in such currencies, which means that the Fund’s NAV or current income could decline as a result of changes in the exchange rates between foreign currencies and the U.S. dollar. In addition, the value of a Fund’s assets may be affected by losses and other expenses incurred in converting between various currencies in order to purchase and sell foreign denominated non-U.S. securities, and by currency restrictions, exchange control regulation, currency devaluations and political and economic developments. Certain investments in non-U.S. securities also may be subject to foreign withholding taxes on dividends, interest, capital gain or other income. Those taxes will decrease a Fund’s yield on any such securities. See the “Taxation” section below. The foregoing risks often are heightened for investments in smaller, emerging capital markets. In addition, individual foreign economies may differ favorably or unfavorably from the U.S. economy in such respects as growth of gross domestic product, rates of inflation, capital reinvestment, resources, self-sufficiency and balance of payments position.

As a result of these potential risks, the Adviser or Sub-Adviser, as applicable, may determine that, notwithstanding otherwise favorable investment criteria, it may not be practicable or appropriate to invest in a particular country. A Fund may invest in countries in which foreign investors, including the Adviser or Sub-Adviser, as applicable, have had no or limited prior experience.

Investing in securities of issuers tied economically to emerging markets entails all of the risks of investing in securities of non-U.S. issuers detailed above to a heightened degree. These heightened risks include: (i) greater risks of expropriation, confiscatory taxation, nationalization, and less social, political

31

Description of Principal Risks

and economic stability; (ii) the smaller size of the markets for such securities and a lower volume of trading, resulting in lack of liquidity and in price volatility; (iii) greater fluctuations in currency exchange rates; and (iv) certain national policies that may restrict a Fund’s investment opportunities, including restrictions on investing in issuers or industries deemed sensitive to relevant national interests.

Ongoing Monitoring Risk. On behalf of the several Lenders, the Agent generally will be required to administer and manage the Senior Loans and, with respect to collateralized Senior Loans, to service or monitor the collateral. In this connection, the valuation of assets pledged as collateral will reflect market value and the Agent may rely on independent appraisals as to the value of specific collateral. The Agent, however, may not obtain an independent appraisal as to the value of assets pledged as collateral in all cases. Floating Rate Opportunities Fund normally will rely primarily on the Agent (where the Fund is a Primary Lender or owns an Assignment) or the selling Lender (where the Fund owns a Participation) to collect principal of and interest on a Senior Loan. Furthermore, the Fund usually will rely on the Agent (where the Fund is a Primary Lender or owns an Assignment) or the selling Lender (where the Fund owns a Participation) to monitor compliance by the Borrower with the restrictive covenants in the Loan Agreement and notify the Fund of any adverse change in the Borrower’s financial condition or any declaration of insolvency. Collateralized Senior Loans will frequently be secured by all assets of the Borrower that qualify as collateral, which may include common stock of the Borrower or its subsidiaries. Additionally, the terms of the Loan Agreement may require the Borrower to pledge additional collateral to secure the Senior Loan, and enable the Agent, upon proper authorization of the Lenders, to take possession of and liquidate the collateral and to distribute the liquidation proceeds pro rata among the Lenders. If the terms of a Senior Loan do not require the Borrower to pledge additional collateral in the event of a decline in the value of the original collateral, the Fund will be exposed to the risk that the value of the collateral will not at all times equal or exceed the amount of the Borrower’s obligations under the Senior Loan. Lenders that have sold Participation interests in such Senior Loan will distribute liquidation proceeds received by the Lenders pro rata among the holders of such Participations. Unless, under the terms of the loan, the Fund has direct recourse against the Borrower, the Fund may have to rely on the Agent or other financial intermediary to apply appropriate credit remedies against a Borrower. The Adviser will also monitor these aspects of the Fund’s investments and, where the Fund is a Primary Lender or owns an Assignment, will be directly involved with the Agent and the other Lenders regarding the exercise of credit remedies.

Options Risk. The use of options is a highly specialized activity which involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. For example, there are significant differences between the securities and options markets that could result in an imperfect correlation between these markets, causing a given transaction not to achieve its objectives. A transaction in options or securities may be unsuccessful to some degree because of market behavior or unexpected events.

When a Fund writes a covered call option, the Fund forgoes, during the option’s life, the opportunity to profit from increases in the market value of the security covering the call option above the sum of the premium and the strike price of the call, but retains the risk of loss should the price of the underlying security decline. The writer of an option has no control over the time when it may be required to fulfill its obligation and once an option writer has received an exercise notice, it must deliver the underlying security at the exercise price.

When a Fund writes a covered put option, the Fund bears the risk of loss if the value of the underlying stock declines below the exercise price minus the put premium. If the option is exercised, the Fund could incur a loss if it is required to purchase the stock underlying the put option at a price greater than the market price of the stock at the time of exercise plus the put premium the Fund received when it wrote the option. Special tax rules apply to a Fund’s or an underlying Fund’s transactions in options, which could increase the amount of taxes payable by shareholders. While a Fund’s potential gain in writing a covered put option is limited to distributions earned on the liquid assets securing the put option plus the premium received from the purchaser of the put option, the Fund risks a loss equal to the entire exercise price of the option minus the put premium.

Payment-in-Kind Securities Risk. The value of PIKs held by Floating Rate Opportunities Fund may be more sensitive to fluctuations in interest rates than other securities. PIKs pay all or a portion of their interest or dividends in the form of additional securities. Federal tax law requires that the interest on PIK bonds be accrued as income to the Fund regardless of the fact that the Fund will not receive cash until such securities mature. Since the income must be distributed to shareholders, the Fund may be forced to liquidate other securities in order to make the required distribution.

Portfolio Turnover Risk. A high rate of portfolio turnover (i.e., 100% or more) will result in increased transaction costs for a Fund in the form of increased dealer spreads and brokerage commissions. Greater transaction costs may reduce Fund performance. High portfolio turnover also may result in increased realization of net short-term capital gains (which are taxable to shareholders as ordinary income when distributed to them), higher taxable distributions and lower a Fund’s after-tax performance.

Prepayment Risk. Borrowers may pay back principal before the scheduled due date. Such prepayments may require Floating Rate Opportunities Fund to replace a debt security with a lower-yielding security. During periods of falling interest rates, issuers of debt securities may repay higher rate securities before their maturity dates. This may cause the Fund to lose potential price appreciation and to be forced to reinvest the unanticipated proceeds at lower interest rates. This may adversely affect the NAV of the Fund’s shares.

Regulatory Risk. Legal, tax and regulatory changes could occur and may adversely affect the Funds and their ability to

32

Highland Funds I Prospectus

October 31, 2013

pursue its investment strategies and/or increase the costs of implementing such strategies. New (or revised) laws or regulations may be imposed by the CFTC, the SEC, the IRS, the U.S. Federal Reserve or other banking regulators, other governmental regulatory authorities or self-regulatory organizations that supervise the financial markets that could adversely affect the Funds. In particular, these agencies are empowered to promulgate a variety of new rules pursuant to financial reform legislation in the United States. The Funds also may be adversely affected by changes in the enforcement or interpretation of existing statutes and rules by these governmental regulatory authorities or self-regulatory organizations.

To the extent that legislation or state or federal regulators impose additional requirements or restrictions with respect to the ability of financial institutions to make loans in connection with highly leveraged transactions, the availability of Senior Loan interests for investment by Floating Rate Opportunities Fund may be adversely affected. In addition, such requirements or restrictions may reduce or eliminate sources of financing for affected Borrowers. Further, to the extent that legislation or federal or state regulators require such institutions to dispose of Senior Loan interests relating to highly leveraged transactions or subject such Senior Loan interests to increased regulatory scrutiny, such financial institutions may determine to sell Senior Loan interests in a manner that results in a price that, in the opinion of the Adviser, is not indicative of fair value. Were the Fund to attempt to sell a Senior Loan interest at a time when a financial institution was engaging in such a sale with respect to the Senior Loan interest, the price at which the Fund could consummate such a sale might be adversely affected. See “Industry Concentration Risk” above.

Risk of Substantial Redemptions. If substantial numbers of shares in a Fund were to be redeemed at the same time or at approximately the same time, a Fund might be required to liquidate a significant portion of its investment portfolio quickly to meet the redemptions. A Fund might be forced to sell portfolio securities at prices or at times when it would otherwise not have sold them, resulting in a reduction in a Fund’s NAV per share; in addition, a substantial reduction in the size of a Fund may make it difficult for the Adviser to execute its investment program successfully for a Fund for a period following the redemptions. If substantial, unexpected redemptions occur, a Fund could experience higher expenses than those shown in the Annual Fund Operating Expenses Tables.

Securities Lending Risk. A Fund will continue to receive interest on any securities loaned while simultaneously earning interest on the investment of the cash collateral in short-term money market instruments. However, a Fund will normally pay lending fees to broker-dealers and related expenses from the interest earned on such invested collateral. Any decline in the value of a portfolio security that occurs while the security is out on loan is borne by the Fund, and will adversely affect performance. There may be risks of delay in receiving additional collateral or risks of delay in recovery of the securities, loss of rights in the collateral should the borrower of the securities fail financially and possible investment losses in the investment of collateral. Any loan may be terminated by either party upon reasonable notice to the other party.

Securities Market Risk. Securities market risk is the risk that the value of securities owned by a Fund may go up or down, sometimes rapidly or unpredictably, due to factors affecting particular companies or the securities markets generally. The profitability of a Fund substantially depends upon the Adviser or Sub-Adviser, as applicable, to correctly assessing the future price movements of stocks, bonds, loans, options on stocks, and other securities and the movements of interest rates. The Adviser or Sub-Adviser, as applicable, cannot guarantee that it will be successful in accurately predicting price movements.

The market prices of equities may decline for reasons that directly relate to the issuing company (such as poor management performance or reduced demand for its goods or services), factors that affect a particular industry (such as a decline in demand, labor or raw material shortages, or increased production costs) or general market conditions not specifically related to a company or industry (such as real or perceived adverse economic conditions, changes in the general outlook for corporate earnings, changes in interest or currency rates, or adverse investor sentiment generally). See also “Debt Securities Risk” above.

As a result of the nature of a Fund’s investment activities, it is possible that the Fund’s financial performance may fluctuate substantially from period to period. Additionally, at any point in time an investment in a Fund may be worth less than the original investment, even after taking into account the reinvestment of dividends and distributions.

Senior Loans Risk. Senior loans may not be rated by a rating agency, registered with the Securities and Exchange Commission or any state securities commission or listed on any national securities exchange. Therefore, there may be less publicly available information about them than for registered or exchange-listed securities.

The risks associated with Senior Loans are similar to the risks of below investment grade securities. Floating Rate Opportunities Fund’s investments in Senior Loans are typically below investment grade and are considered speculative because of the credit risk of their issuers. Also, because portfolio management relies mainly on its own evaluation of the creditworthiness of borrowers, Floating Rate Opportunities Fund is particularly dependent on portfolio management’s analytical abilities. Moreover, any specific collateral used to secure a loan may decline in value or lose all its value or become illiquid, which would adversely affect the loan’s value. Economic and other events, whether real or perceived, can reduce the demand for certain Senior Loans or Senior Loans generally, which may reduce market prices and cause the Fund’s NAV per share to fall. The frequency and magnitude of such changes cannot be predicted.

The secondary market in which these investments are traded is generally less liquid than the market for higher-grade debt. Less liquidity in the secondary trading market could adversely affect the price at which the Fund could sell a high yield Senior

33

Description of Principal Risks

Loan, and could adversely affect the NAV of the Fund’s shares. At times of less liquidity, it may be more difficult to value high yield Senior Loans because this valuation may require more research, and elements of judgment may play a greater role in the valuation since there is less reliable, objective data available. Investments in Senior Loans and other securities may result in greater NAV fluctuation than if the Fund did not make such investments. See “Taxation” below for a discussion of special tax consequences associated with any investment by the Fund in below investment grade securities.

Senior Loans and other debt securities are also subject to the risk of price declines due to increases in prevailing interest rates, although floating rate debt instruments are less exposed to this risk than fixed rate debt instruments. Conversely, the floating rate feature of Senior Loans means the Senior Loans will not generally experience capital appreciation in a declining interest rate environment. Declines in interest rates may also increase prepayments of debt obligations and require the Fund to invest assets at lower yields. No active trading market may exist for certain Senior Loans, which may impair the ability of the Fund to realize full value in the event of the need to liquidate such assets. Adverse market conditions may impair the liquidity of some actively traded Senior Loans.

Although Senior Loans in which the Fund will invest will often be secured by collateral, there can be no assurance that liquidation of such collateral would satisfy the Borrower’s obligation in the event of a default or that such collateral could be readily liquidated. In the event of bankruptcy of a Borrower, the Fund could experience delays or limitations in its ability to realize the benefits of any collateral securing a Senior Loan. The Fund may also invest in Senior Loans that are not secured.

In addition to the risks typically associated with debt securities and loans generally, Senior Loans are also subject to the risk that a court could subordinate a Senior Loan, which typically holds a senior position in the capital structure of a borrower, to presently existing or future indebtedness or take other action detrimental to the holders of Senior Loans.

Short Sales Risk. Short sales by each Fund that are not made “against-the-box” (that is when a Fund has an offsetting long position in the asset that is selling short) theoretically involve unlimited loss potential since the market price of securities sold short may continuously increase. When a Fund engages in a short sale on a security, it must borrow the security sold short and deliver it to the counterparty. A Fund will ordinarily have to pay a fee or premium to borrow particular securities and be obligated to repay the lender of the security any dividends or interest that accrue on the security during the period of the loan. The amount of any gain from a short sale will be decreased, and the amount of any loss increased, by the amount of the premium, dividends, interest or expenses a Fund pays in connection with the short sale. Short selling allows a Fund to profit from declines in market prices to the extent such decline exceeds the transaction costs and the costs of borrowing the securities. However, since the borrowed securities must be replaced by purchases at market prices in order to close out the short position, any appreciation in the price of the borrowed securities would result in a loss. Purchasing securities to close out the short position can itself cause the price of the securities to rise further, thereby exacerbating the loss. A Fund may mitigate such losses by replacing the securities sold short before the market price has increased significantly. Under adverse market conditions, a Fund might have difficulty purchasing securities to meet its short sale delivery obligations, and might have to sell portfolio securities to raise the capital necessary to meet its short sale obligations at a time when fundamental investment considerations would not favor such sales. See “Taxation” below for special tax considerations associated with engaging in short sales.

Style Risk. Securities with different characteristics tend to shift in and out of favor depending upon market and economic conditions as well as investor sentiment. The Fund may underperform other funds that employ a different style. A Fund also may employ a combination of styles that impact its risk characteristics. Examples of different styles include growth and value investing, as well as those focusing on large, medium, or small company securities.

34

Highland Funds I Prospectus

October 31, 2013

Management of the Funds