X0609 4 2026-05-07 0001766368 Mayville Engineering Company, Inc. MEC 0001937748 Reddy Jagadeesh A false 135 SOUTH 84TH STREET SUITE 300 MILWAUKEE WI 53214 true true false false President & CEO true Common Stock 2026-05-07 4 S false 10332 25.72 D 169851 D Common Stock 2026-05-07 4 S false 11464 26.11 D 158387 D Common Stock 2300 I by ESOP and/or 401(k) Plan Common Stock 380 I By Daughter Restricted Stock Units 0 Common Shares 36317 36317 D Restricted Stock Units 0 Common Shares 55284 55284 D Restricted Stock Units 0 Common Shares 74986 74986 D Stock Option (right to buy) 16.22 Common Shares 88901 88901 D The reported transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on December 12, 2025. The price in Column 4 is a weighted average price. The prices actually received ranged from $25.00 to $25.99. The reporting person has provided to the issuer, and will provide to any security holder of the issuer, or the SEC staff, upon request, information regarding the number of shares sold at each price within the range for all transactions reported in this Form 4 utilizing a weighted average price. The price in Column 4 is a weighted average price. The prices actually received ranged from $26.00 to $26.28. The reporting person has provided to the issuer, and will provide to any security holder of the issuer, or the SEC staff, upon request, information regarding the number of shares sold at each price within the range for all transactions reported in this Form 4 utilizing a weighted average price. Reflects the most recent ESOP and 401(k) balance. The restricted stock units will vest 1/3 on each of March 15, 2025, 2026 and 2027. The restricted stock units will vest 1/3 on each of March 15, 2026, 2027 and 2028. The restricted stock units will vest 1/3 on each of March 15, 2027, 2028 and 2029. The options will vest 50% on each of February 28, 2024 and February 28, 2025. /s/ Garrett F. Bishop, Attorney-in-Fact for Jagadeesh A. Reddy 2026-05-11