As filed with the Securities and Exchange Commission on March 25, 2015

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

FRANKLIN FINANCIAL NETWORK, INC.

(Exact name of registrant as specified in its charter)

722 Columbia Avenue

Franklin, Tennessee 37064

(615) 236-2265

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Richard E. Herrington

President and Chief Executive Officer

Franklin Financial Network, Inc.

722 Columbia Avenue

Franklin, Tennessee 37064

(615) 236-2265

(Name, address, including zip code, and telephone number, including area code of agent for service)

Approximate date of commencement of the proposed sale of the securities to the public: As soon as practicable after this registration statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  x  (File No. 333-201528)

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer,” “non-accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

This Registration Statement shall become effective upon filing in accordance with Rule 462(b) under the Securities Act of 1933.

EXPLANATORY NOTE AND INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

This Registration Statement on Form S-1 is being filed with the Securities and Exchange Commission (the “Commission”) pursuant to Rule 462(b) under the Securities Act of 1933, as amended. This Registration Statement incorporates by reference the contents of, including all amendments and exhibits thereto, the Registration Statement on Form S-1 (Registration No. 333-201528), which was declared effective by the Commission on March 25, 2015, and is being filed solely for the purpose of registering an increase in the amount of shares of common stock registered by 276,000 shares. The required opinions and consents are listed on the Exhibit Index attached hereto and filed herewith.

SIGNATURES

Pursuant to the requirements of the Securities Act, the Registrant has duly caused this Registration Statement to be signed on its behalf by the undersigned, hereunto duly authorized, in the City of Franklin, State of Tennessee on March 25, 2015.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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