8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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):May 26, 2022

BAIN CAPITAL SPECIALTY FINANCE, INC.

(Exact name of Registrant as Specified in ItsCharter)

Registrant’s telephone number, includingarea code: (617) 516-2000

(Former Name or Former Address, if ChangedSince 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 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

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. ¨

Securities registered pursuant to Section 12(b) of the Act:

Item 5.07. Submission of Matters to a Vote of Security Holders.

On May 26, 2022, Bain Capital Specialty Finance, Inc. (the “Company”) held its 2022 Annual Meeting of Stockholders (the “Annual Meeting”). At the Annual Meeting, stockholders considered two proposals as described in the Company’s proxy statement filed on April 15, 2022. As of the record date, April 11, 2022, there were 64,562,265.27 shares of issued and outstanding shares of common stock entitled to vote at the Annual Meeting. The final voting results on the matter submitted to stockholders at the Annual Meeting are set forth below.

Proposal I: By the vote shown below, the stockholders elected both David G. Fubini and Jeffrey B. Hawkins, each as a Class III Director, both of whom will serve until the 2025 annual meeting of the stockholders or until their respective successor is duly elected and qualified. The election of each nominee required a majority of the votes cast by all stockholders present, in person or by proxy, at the Annual Meeting.

Proposal II: By the vote shown below, the stockholders renewed the Company’s authorization, with approval from the Company’s Board of Directors, to sell shares of the Company’s common stock at a price below the then-current net asset value per share, subject to certain limitations.

SIGNATURES

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