Exhibit 23.1 

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in this Registration Statement on Form S-3 of SELLAS Life Sciences Group, Inc. (the “Company”), of our report dated March 28, 2024, relating to the consolidated financial statements of the Company (which report expresses an unqualified opinion and includes an explanatory paragraph relating to a going concern emphasis), appearing in the Annual Report on Form 10-K of the Company for the year ended December 31, 2023, filed with the Securities and Exchange Commission. We also consent to the reference to us under the heading “Experts” in such Registration Statement.

/s/ Moss Adams LLP

Campbell, California

March 28, 2024