UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT PURSUANT TO

SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): September 13, 2018

CAPSTAR FINANCIAL HOLDINGS, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code     (615) 732-6400

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2). Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

CapStar Financial Holdings, Inc., a Tennessee corporation (“CapStar”), has received all required regulatory approvals, including the approval of the Board of Governors of the Federal Reserve System and the Tennessee Department of Financial Institutions, necessary to consummate the acquisition of Athens Bancshares Corporation, a Tennessee corporation (“Athens”), pursuant to the Agreement and Plan of Merger, dated as of June 11, 2018, by and between CapStar and Athens.

Subject to the satisfaction of customary closing conditions, the transaction is anticipated to be completed on October 1, 2018.

Forward Looking Statements

This report contains “forward-looking statements” within the meaning of the federal securities laws, including Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. These forward-looking statements may include: management plans relating to the proposed transaction; the expected timing of the completion of the proposed transaction; the ability to complete the proposed transaction; and any statements of assumptions underlying any of the foregoing. Forward-looking statements are typically identified by words such as “believe,” “expect,” “anticipate,” “intend,” “seek,” “plan,” “will,” “would,” “target,” “outlook,” “estimate,” “forecast,” “project” and other similar words and expressions or negatives of these words. Forward-looking statements are subject to numerous assumptions, risks and uncertainties, which change over time and are beyond CapStar’s control. Because forward-looking statements are by their nature, to different degrees, uncertain and subject to assumptions, actual results or future events could differ, possibly materially, from those that CapStar anticipated in its forward-looking statements, and future results could differ materially from historical performance. Factors that could cause or contribute to such differences include, but are not limited to, those included under Item 1A “Risk Factors” in CapStar’s Annual Report on Form 10-K for the year ended December 31, 2017 and those disclosed in CapStar’s other periodic reports filed with the Securities and Exchange Commission (the “SEC”), as well as the possibility that expected benefits of the proposed transaction may not materialize in the time frame expected or at all, or may be more costly to achieve; the proposed transaction may not be timely completed, if at all; that prior to the completion of the proposed transaction or thereafter, CapStar’s and Athens’s respective businesses may not perform as expected due to transaction-related uncertainty or other factors; that the parties are unable to successfully implement integration strategies related to the proposed transaction; that customary closing conditions are not satisfied in a timely manner or at all; reputational risks and the reaction of the companies’ shareholders, customers, employees or other constituents to the proposed transaction; and diversion of management time on merger-related matters. These risks, as well as other risks associated with the proposed transaction, were more fully discussed in the joint proxy statement/prospectus that was included in the registration statement on Form S-4 filed with the SEC in connection with the proposed transaction. While the list of factors presented here is considered representative, no such lists should be considered to be a complete statement of all potential risks and uncertainties. Unlisted factors may present significant additional obstacles to the realization of forward-looking statements. For any forward-looking statements made in this communication or in any documents, CapStar claims the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

Forward-looking statements speak only as of the date they are made. CapStar does not undertake any obligation to update any forward-looking statement to reflect circumstances or events that occur after the date on which the forward-looking statement is made.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: September 17, 2018