We describe SGC-GAK-1 (11), a potent, selective, and cell-active inhibitor of cyclin G-associated kinase (GAK), together with a structurally related negative control SGC-GAK-1N (14). 11 was highly selective in an in vitro kinome-wide screen, but cellular engagement assays defined RIPK2 as a collateral target. We identified 18 as a potent RIPK2 inhibitor lacking GAK activity. Together, this chemical probe set can be used to interrogate GAK cellular biology.