X0306 4 2020-06-05 0 0001370450 Willdan Group, Inc. WLDN 0001395188 Brisbin Thomas Donald 2401 EAST KATELLA AVENUE SUITE 300 ANAHEIM CA 92806 1 1 0 1 Chief Executive Officer Chairman of the Board Common Stock 2020-06-05 4 M 0 19878 2.71 A 238337 D Common Stock 2020-06-05 4 S 0 11037 27.78 D 227300 D Common Stock 2020-06-08 4 M 0 22459 2.71 A 249759 D Common Stock 2020-06-08 4 S 0 12465 27.39 D 237294 D Common Stock 2020-06-09 4 M 0 7663 2.71 A 244957 D Common Stock 2020-06-09 4 S 0 4261 26.31 D 240696 D Stock Options (Right to Buy) 2.71 2020-06-05 4 M 0 19878 0 D 2020-08-12 Common Stock 19878 30122 D Stock Options (Right to Buy) 2.71 2020-06-08 4 M 0 22459 0 D 2020-08-12 Common Stock 22459 7663 D Stock Options (Right to Buy) 2.71 2020-06-09 4 M 0 7663 0 D 2020-08-12 Common Stock 7663 0 D The price reported in Column 4 is the weighted average price. These shares were sold in multiple transactions at prices ranging from $27.30 to $28.16, inclusive. The reporting person undertakes to provide to Willdan Group, Inc., any security holder of Willdan Group, Inc., 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 footnotes (1), (2) and (3). The price reported in Column 4 is the weighted average price. These shares were sold in multiple transactions at prices ranging from $27.24 to $28.18, inclusive. The price reported in Column 4 is the weighted average price. These shares were sold in multiple transactions at prices ranging from $26.04 to $26.52, inclusive. Stock options granted under the Willdan Group, Inc. Amended and Restated 2008 Performance Incentive Plan, which vested in three equal installments on each of August 12, 2011, August 12, 2012 and August 12, 2013. /s/ Stacy McLaughlin Attorney-in-Fact for Thomas D. Brisbin 2020-06-09