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): November 20, 2023

New Mountain Guardian III BDC, L.L.C.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (212) 720-0300

None

(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):

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

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).

x 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. ¨

On November 20, 2023, the Board of Directors of New Mountain Guardian III BDC, L.L.C. (the “Company”) appointed Kris Corbett as the Chief Financial Officer and Treasurer of the Company, effective as of November 27, 2023. Laura C. Holson, who has served as the Company’s interim Chief Financial Officer and Treasurer since April 1, 2023, will relinquish such positions upon the effective date of Mr. Corbett’s appointment. Ms. Holson will continue to serve as the Company’s Chief Operating Officer.

Mr. Corbett previously served as a Senior Vice President, Controller and Treasurer of both Blackstone Private Credit Fund and Blackstone Secured Lending Fund. Prior to joining Blackstone in 2016, Mr. Corbett was a Managing Director at Perella Weinberg Partners where he performed roles in finance, accounting and financial reporting within alternative asset management. Prior to Perella Weinberg Partners, Mr. Corbett held a variety of positions in accounting and financial reporting at King Street Capital Management and Ziff Brothers Investments. He began his career in public accounting at Pricewaterhouse Coopers. Mr. Corbett received a Bachelor of Business Administration in Accounting from University of Massachusetts and is a Certified Public Accountant in the state of New York and a CFA Charterholder. There is no arrangement or understanding between Mr. Corbett and any other person pursuant to which he was appointed as the Chief Financial Officer and Treasurer.

d) Exhibits.

SIGNATURE

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