Exhibit 31.3

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Marec E. Edgar, President and Chief Executive Officer (Principal Executive Officer), do hereby certify that:

(1)I have reviewed this Amendment to the annual report on Form 10-K/A of A.M. Castle and Co.; and

(2)Based on my knowledge, this report does not contain any untrue statement of material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.

/s/ Marec E. Edgar

Marec E. Edgar

President and Chief Executive Officer

March 19, 2020