X0306 4 2022-02-22 0000354190 Arthur J. Gallagher & Co. AJG 0001589933 GALLAGHER THOMAS JOSEPH 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 VICE PRESIDENT Common Stock 2022-02-22 4 M 0 26800 46.17 A 285605 D Common Stock 2022-02-22 4 M 0 10000 43.71 A 295605 D Common Stock 2022-02-22 4 S 0 36800 153.24 D 258805 D Common Stock 96007 I By grantor retained annuity trust Common Stock 66709 I By Irrevocable Trust Common Stock 31671 I By wife Common Stock 89960 I By wife as trustee Common Stock 121.1 I Gallagher 401(k) plan account Non-qualified Stock Option 46.17 2022-02-22 4 M 0 26800 0 D 2022-03-11 Common Stock 26800 0 D Non-qualified Stock Option 43.71 2022-02-22 4 M 0 10000 0 D 2023-03-17 Common Stock 10000 25400 D The price reported is an average weighted price. The shares were sold in multiple transactions at prices ranging from $153.07 to $153.41. The reporting person will provide to the Securities and Exchange Commission staff, the issuer, or any security holder of the issuer, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The reporting person disclaims beneficial ownership of these shares, and this report shall not be deemed an admission that the reporting person is the beneficial owner of these shares for purposes of Section 16 or for any other purpose. These shares are held in trusts, for the benefit of the reporting person's children, of which his wife is a trustee. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. /s/ Seth Diehl, by power of attorney 2022-02-24