SUMMARY

This summary highlights material information regarding the merger, the FFN annual shareholders’ meeting and the MidSouth special shareholders’ meeting contained later in this joint proxy statement/prospectus. This summary does not contain all of the information that may be important to you, and we urge you to carefully read this entire document, including the exhibits and enclosures, to better understand the merger and its potential impact on you before deciding how to vote. Each item in this summary includes a page reference directing you to a more complete discussion of the item.

The Companies (page 104 for FFN and page 157 for MidSouth)

Franklin Financial Network, Inc.

722 Columbia Avenue

Franklin, Tennessee 37064

(615) 236-2265

Attention: Richard E. Herrington, President and Chief Executive Officer

FFN is a Tennessee corporation registered as a bank holding company under the Federal Reserve Act. FFN engages in a general banking business through its subsidiary, FSB, a Tennessee state bank, which commenced operations on November 5, 2007. The executive offices of FFN and FSB are located in Franklin, Tennessee. FSB has branches in the cities of Brentwood, Spring Hill and the Cool Springs, Westhaven and Berry Farms communities of Franklin, Tennessee. FSB also has a mortgage loan production office in Brentwood, Tennessee.

MidSouth Bank

One East College Street

Murfreesboro, TN 37130

(615) 278-7100

Attention: Lee M. Moss, Chief Executive Officer

MidSouth opened as a full-service commercial bank in January 2004. Its principal business activity is providing banking services to Rutherford County and surrounding areas in the Nashville-Davidson-Murfreesboro-Franklin, Tennessee Metropolitan Statistical Area. The principal executive offices of MidSouth are located in Murfreesboro, Tennessee.

The Merger (page 78)

Under the terms of the merger agreement, MidSouth will merge with and into FSB, with FSB as the surviving Tennessee banking corporation. Both FFN and FSB will continue their existence under Tennessee law, while MidSouth will cease to exist. The merger agreement is attached as Appendix A and is incorporated into this joint proxy statement/prospectus by reference. We encourage you to read the merger agreement carefully as it is the legal document that governs the merger.

What MidSouth Shareholders Will Receive in the Merger (page 78)

If the merger is completed, each share of MidSouth common stock will be converted into the right to receive 0.425926 shares of FFN common stock; each share of MidSouth preferred stock will be converted into the right to receive 0.851852 shares of FFN common stock; each warrant to purchase shares of MidSouth common stock will be converted into that number of shares of FFN common stock equal to (i) $5.75 less the strike price of the warrant at the effective date of the merger (ii) divided by $13.50; and each option to purchase a share of MidSouth common stock will be converted into an option to purchase a share of FFN common stock multiplied by the exchange ratio of one share of MidSouth common stock equating to 0.425926 shares of FFN common stock (the “Exchange Ratio”) and the exercise price will become the exercise price of such option divided by the Exchange Ratio. Options to acquire MidSouth common stock that are considered “qualified” options will be converted into qualified options of FFN common stock and options to purchase MidSouth stock that are not “qualified” will be converted into non-qualified options to acquire FFN common stock. In lieu of the issuance of any fractional shares of FFN common stock, FFN will pay to each former MidSouth shareholder who would otherwise be entitled to

receive such fractional share an amount in cash determined by multiplying (i) $13.50 by (ii) the fraction of a share (rounded to the nearest thousandth when expressed in decimal form) of FFN common stock to which such holder would otherwise be entitled to receive.

Regulatory Approvals (page 64)

For the merger of MidSouth with and into FSB, we must obtain approval from the Federal Reserve Board (the “FRB”) and from the Tennessee Department of Financial Institutions (“TDFI”). FFN and MidSouth received approval from the FRB on January 28, 2014. As of the date of this joint proxy statement/prospectus, FFN and MidSouth have not received approval from the TDFI.

FFN’s Annual Shareholders’ Meeting (page 38)

FFN will hold its annual shareholders’ meeting on                     , 2014, at         .m., local time at 722 Columbia Avenue, Franklin, Tennessee.

FFN’s Record Date and Voting (pages 38-40)

If you owned shares of FFN common stock at the close of business on                     , 2014, the record date for the FFN annual shareholders’ meeting, you are entitled to vote on the FFN merger proposal, the election of seven directors to serve until the 2015 annual meeting of shareholders, the ratification of the selection of Crowe Horwath LLP as FFN’s independent registered public accounting firm for 2014, the amendment of FFN’s 2007 Omnibus Equity Incentive Plan to increase the number of shares of FFN’s common stock available for issuance under the plan from 1,500,000 to 2,000,000, the authorization of the board of directors to adjourn the annual shareholders’ meeting to allow time for further solicitation of proxies in the event there are insufficient votes present at the annual shareholders’ meeting, in person or by proxy, to approve any of the matters to be considered at the annual meeting, as well as any other matters considered at the annual shareholders’ meeting. On the record date, there were              shares of FFN common stock outstanding. You will have one vote at the meeting for each share of FFN common stock you owned on the record date.

Approval of the FFN merger proposal requires the affirmative vote of the holders of a majority of the outstanding shares of FFN common stock entitled to vote at the annual shareholders’ meeting. Directors will be elected by a plurality of the votes cast by holders of shares entitled to vote at the annual meeting. Approval of each of the ratification of the selection of Crowe Horwath LLP as FFN’s independent registered public accounting firm for 2014, the amendment of FFN’s 2007 Omnibus Equity Incentive Plan and the proposal to authorize adjournment requires the affirmative vote of the holders of a majority of shares of common stock present in person or by proxy and entitled to vote on such matters. As of                     , 2014, FFN’s current directors, executive officers, and their affiliates beneficially owned approximately     % of the outstanding shares of common stock.

MidSouth’s Record Date and Voting (pages 38-40)

If you owned shares of MidSouth common stock or preferred stock at the close of business on                     , 2014, the record date for the MidSouth special shareholders’ meeting, you are entitled to vote on the merger agreement as well as any other matters considered at the special shareholders’ meeting. On the record date, there were             shares of MidSouth voting stock outstanding. You will have one vote at the meeting for each share of MidSouth voting stock you owned on the record date. Approval of the merger agreement requires the affirmative vote of the holders of a majority of the outstanding shares of the MidSouth voting stock entitled to vote at the special shareholders’ meeting. Approval of the proposal to authorize adjournment will require the affirmative vote of a majority of shares of MidSouth voting stock present in person or by proxy and entitled to vote on the matter. As of                     , 2014, MidSouth’s directors and executive officers and their affiliates beneficially owned approximately         % of the outstanding shares of MidSouth voting stock.

FFN’s Board of Directors Unanimously Recommends that FFN Shareholders Vote “FOR” the Approval of the FFN Merger Proposal (page 41)

FFN’s board of directors has determined that the FFN merger proposal is advisable and in the best interests of FFN and its shareholders and has unanimously approved the merger agreement. FFN’s board of directors unanimously recommends that FFN shareholders vote “ FOR ” the approval of the FFN merger proposal. For the factors considered by FFN’s board of directors in reaching its decision to approve the FFN merger proposal, see “FFN AND MIDSOUTH PROPOSAL NO. 1—THE MERGER—FFN’s Reasons for the FFN Merger Proposal; Recommendation of the FFN Merger Proposal by the FFN Board of Directors.”

MidSouth’s Board of Directors Unanimously Recommends that MidSouth Shareholders Vote “FOR” the Approval of the Merger Agreement (page 42)

MidSouth’s board of directors has determined that the merger, the merger agreement and the transactions contemplated by the merger agreement are advisable and in the best interests of MidSouth and its shareholders and has adopted the merger agreement. MidSouth’s board of directors recommends that MidSouth shareholders vote “ FOR ” the approval of the merger agreement. For the factors considered by MidSouth’s board of directors in reaching its decision to adopt the merger agreement, see “FFN AND MIDSOUTH PROPOSAL NO. 1—THE MERGER—MidSouth’s Reasons for the Merger; Recommendation of the Merger by the MidSouth Board of Directors.”

Interests of Directors and Officers of MidSouth that Differ from Your Interests (page 63)

When considering whether to approve the merger agreement, you should be aware that some directors and officers of MidSouth have interests in the merger that differ from the interests of other MidSouth shareholders, including the following:

Each MidSouth board member was aware of these and other interests and considered them before approving and adopting the merger agreement.

Federal Income Tax Consequences (page 74)

If the merger qualifies as a reorganization under Section 368(a) of the Internal Revenue Code, a MidSouth shareholder will generally not recognize any gain or loss on the conversion of shares of MidSouth common stock,

preferred stock or warrants into shares of FFN common stock. FFN shareholders will have no direct tax consequences as a result of the merger. Tax matters are complicated, and the tax consequences of the merger may vary among MidSouth shareholders. We urge each MidSouth shareholder to contact his or her own tax advisor to fully understand the tax implications of the merger.

Comparative Rights of Shareholders (page 103)

The rights of MidSouth’s shareholders are currently governed by Tennessee corporate law and MidSouth’s charter and bylaws. The rights of FFN’s shareholders are currently governed by Tennessee corporate law and FFN’s charter and bylaws. Upon consummation of the merger, the shareholders of MidSouth will become shareholders of FFN, and the charter and bylaws of FFN, as well as Tennessee corporate law, will govern their rights. FFN’s charter and bylaws differ somewhat from those of MidSouth.

Termination of the Merger Agreement and Termination Fee (page 84)

Notwithstanding the approval of the merger agreement by MidSouth shareholders and the FFN merger proposal by FFN shareholders, the parties can mutually agree at any time to terminate the merger agreement before completing the merger.

Either FFN or MidSouth can also terminate the merger agreement:

FFN can terminate the merger agreement if MidSouth’s board of directors authorizes, recommends, proposes or publicly announces its intention to authorize, recommend or propose an acquisition proposal with any person other than FFN.

FFN and MidSouth may each terminate the merger agreement at any time upon the payment of liquidated damages of $1.5 million.

Accounting Treatment (page 77)

FFN will account for the merger using the acquisition method of accounting. For accounting purposes, the cost of the “acquired” entity (MidSouth) will be allocated to consolidated tangible and intangible assets and liabilities based on their estimated fair value on the date that the share exchange is completed. Any excess cost will be allocated to goodwill. The financial statements of FFN issued after the merger will reflect the results attributable to the acquired operations of the two banks beginning on the date of completion of the share exchange. The unaudited per share pro forma financial information contained herein has been prepared using the acquisition method of accounting.

Market and Dividend Information (pages 95, 99)

FFN’s common stock is not currently listed or traded on any securities exchange or quotation system. Neither the common stock nor the preferred stock of MidSouth is listed or traded on any securities exchange or quotation system.

The ability of FFN to pay dividends is highly dependent on FSB’s ability to pay dividends and may be limited based upon restrictions of the Small Business Lending Fund. The likelihood of FFN declaring dividends to its shareholders is contingent on the anticipated growth and capital preservation strategy to maintain a strong capital level for both FSB and FFN. As a result, FFN cannot project or guarantee when dividends will be declared in the future.

Resale of FFN Common Stock (page 78)

The shares of FFN common stock to be issued to the shareholders of MidSouth in connection with the merger will be freely tradable by such shareholders, except that if any MidSouth shareholders are deemed to be affiliates of FFN, they must abide by certain transfer restrictions under the Securities Act of 1933, as amended (the “Securities Act”).

Dissenters’ Rights (page 71)

Under Tennessee law, holders of MidSouth common stock and preferred stock will be entitled to dissent from the merger and to obtain payment in cash of the fair value of his or her shares of MidSouth common stock or preferred stock. Set forth below is a summary of the procedures that must be followed by the holders of MidSouth common stock and preferred stock in order to exercise their dissenters’ rights. This summary is qualified in its entirety by reference to the text of the applicable Tennessee statutes, a copy of which are attached to this joint proxy statement/prospectus as Appendix B .

A record holder of MidSouth common stock or preferred stock who wishes to assert dissenters’ rights (i) must deliver to MidSouth, before the vote on the merger agreement is taken, written notice of his or her intent to demand payment for his or her shares if the merger is effectuated and (ii) must not vote his or her shares in favor of the merger agreement.

If the merger is approved at the MidSouth special shareholders’ meeting, MidSouth will deliver, no later than 10 days after the date that the merger is completed, a written dissenters’ notice to all MidSouth shareholders who satisfied the two requirements set forth above. The written dissenters’ notice will state where the payment demand must be sent and where and when stock certificates must be deposited and will set a date by which MidSouth must receive the payment demand, which date will not be less than one nor more than two months after the written dissenters’ notice is delivered. A dissenting shareholder who does not demand payment or deposit his or her share certificate as required by the dissenters’ notice will not be entitled to payment for his or her shares, and such shareholder’s shares of MidSouth stock will be converted into the right to receive the merger consideration in connection with the merger.

Within 10 days of the later of the date of the merger or receipt of a payment demand, MidSouth will, by written notice, offer to pay to each dissenting shareholder who properly demanded payment the amount MidSouth estimates to be the fair value of his or her shares, plus accrued interest. If the shareholder believes that the amount offered is less than the fair value of his shares or that the interest is incorrectly calculated, the shareholder may notify MidSouth in writing of his own estimate of the fair value of his shares and the amount of interest due and demand payment of his estimate. If a demand for payment remains unsettled, MidSouth will commence a court proceeding to determine the fair value of the shares and the accrued interest.

Exercise of dissenters’ rights by holders of MidSouth common stock or preferred stock will result in the recognition of gain or loss, as the case may be, for federal income tax purposes.