Homologous recombination (HR) is a highly conserved pathway that can facilitate the repair of DNA double-strand breaks (DSB). Several Deubiquitinases (DUB) have been implicated as key players in DNA damage repair (DDR) through HR. Here, we report USP22, a DUB that is highly overexpressed in multiple cancer types, is necessary for HR through a direct interaction with PALB2 through its C-terminal WD40 domain. This interaction stimulates USP22 catalytic activity in vitro. Furthermore, we show USP22 is necessary for BRCA2, PALB2, and Rad51 recruitment to DSBs and this is, in part, through USP22 stabilizing BRCA2 and PALB2 levels. Taken together, our results describe a role for USP22 in DNA repair. IMPLICATIONS: This research provides new and exciting mechanistic insights into how USP22 overexpression promotes chemoresistance in lung cancer. We believe this study, and others, will help aid in developing targeted drugs toward USP22 and known binding partners for lung cancer treatment.,©2019 American Association for Cancer Research.