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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 on Form 10-Q of Cartesian Therapeutics, Inc. (the “Company”) for the period ended June 30, 2025 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned officers of the Company hereby certifies, pursuant to 18 U.S.C. Section 1350, that to his knowledge:

1.    The Quarterly Report on Form 10-Q of the Company for the period ended June 30, 2025 (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.

August 7, 2025						/s/ Carsten Brunn, Ph.D.
						Carsten Brunn, Ph.D.
						President and Chief Executive Officer, and Director
						(Principal Executive Officer)

August 7, 2025						/s/ Blaine Davis
						Blaine Davis
						Chief Financial Officer
						(Principal Financial Officer)