FirstMark Acquisition Corp. II S-1 IPO registration

Exhibit 23.1

Independent Registered Public Accounting Firm’s Consent

We consent to the inclusion in this Registration Statement of FirstMark Acquisition Corp. II on Form S-1 of our report dated March 12, 2021, which includes an explanatory paragraph as to the Company’s ability to continue as a going concern, with respect to our audit of the financial statements of FirstMark Acquisition Corp. II as of February 19, 2021 and for the period from February 8, 2021 (inception) through February 19, 2021, which report appears in the Prospectus, which is part of this Registration Statement. We also consent to the reference to our Firm under the heading “Experts” in such Prospectus.

/s/Marcum LLP

Marcum llp

Tampa, FL

March 12, 2021