Exhibit 32.1

CERTIFICATION 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 of John Marshall Bancorp, Inc. (the “Company”) on Form 10-Q for the quarter ended June 30, 2023, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned Chief Executive Officer and Chief Financial Officer of the Company hereby certify, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002 that based on their knowledge and belief: (1) the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, and (2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of and for the periods covered in the Report.

/s/ Christopher W. Bergstrom

Christopher W. Bergstrom

President and Chief Executive Officer

/s/ Kent D. Carstater

Kent D. Carstater

Senior Executive Vice President and Chief Financial Officer

August 9, 2023