Phillip Street Middle Market Lending Fund 10-Q 2024 Q1 Quarterly report

Exhibit 32.3

Certification of Chief Financial Officer

Pursuant to

18 U.S.C. Section 1350 as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

In connection with the Quarterly Report on Form 10-Q of Phillip Street Middle Market Lending Fund LLC (the “Company”) for the quarter ended March 31, 2024 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), Stanley Matuszewski, as Chief Financial Officer of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to the best of his knowledge:

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: May 9, 2024

/s/ Stanley Matuszewski

Stanley Matuszewski

Chief Financial Officer and Treasurer

(Principal Financial Officer)