X0609 4 2026-09-03 0001370450 Willdan Group, Inc. WLDN 0001395188 Brisbin Thomas Donald false 2401 EAST KATELLA AVENUE SUITE 300 ANAHEIM CA 92806 true false false false 0 Common Stock 2026-09-03 4 M 0 58757 16.27 A 155444 D Common Stock 2026-09-03 4 S 0 58757 88.14 D 96687 D Stock Options (Right to Buy) 16.27 2026-09-03 4 M 0 58727 0 D 2017-11-03 2026-11-03 Common Stock 58727 30979 D Includes 1,241 shares of restricted stock that vest on June 17, 2027. The price reported in Column 4 is the weighted average price. These shares were sold in multiple transactions at prices ranging from $88.05 to $88.49, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (2). Stock options granted under the Willdan Group, Inc. Amended and Restated 2008 Performance Incentive Plan, which vested in three equal installments on each of November 3, 2017, November 3, 2018 and November 3, 2019. /s/ Creighton K. Early, Attorney-in-Fact for Thomas D. Brisbin 2026-09-04