EXHIBIT 23.1

Consent of Marcum LLP, Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement ofAcme United Corporation on Form S-8 (File Nos. 333-267800, 333-260112, 333-248739, 333-227147, 333-220282, 333-206440, 333-198220, 333-190623, 333-183351, 333-176314, 333-168801, 333-161392, 333-145516, 333-126478, 333-70348, 333-70346, 333-84505, 333-84509, 333-84499, 333-26739 and 333-26737) of our report dated March 7, 2024, with respect to our audits of the consolidated financial statements of Acme United Corporation and Subsidiaries as of December 31, 2023 and 2022 and for the years then ended and our report dated March 7, 2024 with respect to our audit of internal control over financial reporting of Acme United Corporation and Subsidiaries as of December 31, 2023, which reports are included in this Annual Report on Form 10-K of Acme United Corporation for the year ended December 31, 2023.

Our report on the effectiveness of internal control over financial reporting expressed an adverse opinion because of a material weakness.

/s/ Marcum LLP

Marcum LLP

Boston, Massachusetts

March 7, 2024