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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 this Annual Report of IES Holdings, Inc. (the “Company”) on Form 10-K for the period ending September 30, 2025 (the “Report”), I, Matthew J. Simmes, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

(1)The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and
(2)The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: November 21, 2025By:/s/ MATTHEW J. SIMMES
Matthew J. Simmes
President and Chief Executive Officer as Principal Executive Officer