Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We hereby consent to the incorporation by reference. in the Registration Statements on Form S-8 (Nos. 333-239224, 333-239707, and 333-256466) and Form S-3 (No. 333-264623) of CECO Environmental Corp. (the Company) of our reports dated March 5, 2024, relating to the consolidated financial statements, and the effectiveness of the Company’s internal control over financial reporting, which appear in this Annual Report on Form 10-K. Our report on the effectiveness of internal control over financial reporting expresses an adverse opinion on the effectiveness of the Company’s internal control over financial reporting as of December 31, 2023.

/s/ BDO USA, P.C.

Cincinnati, Ohio

March 5, 2024