Poly(ADP-ribose) polymerase 1 (PARP1) is a DNA damage sensor, which upon activation, recruits downstream proteins by poly(ADP-ribosyl)ation (PARylation). However, it remains largely unclear how PARP1 activity is regulated. Interestingly, the data obtained through this study revealed that PARP1 was co-immunoprecipitated with checkpoint kinase 2 (CHK2), and the interaction was increased after oxidative DNA damage. Moreover, CHK2 depletion resulted in a reduction in overall PARylation. To further explore the functional relationship between PARP1 and CHK2, this study employed H₂O₂ to induce an oxidative DNA damage response in cells. Here, we showed that CHK2 and PARP1 interact in vitro and in vivo through the CHK2 SCD domain and the PARP1 BRCT domain. Furthermore, CHK2 stimulates the PARylation activity of PARP1 through CHK2-dependent phosphorylation. Consequently, the impaired repair associated with PARP1 depletion could be rescued by re-expression of wild-type PARP1 and the phospho-mimic but not the phospho-deficient mutant. Mechanistically, we showed that CHK2-dependent phosphorylation of PARP1 not only regulates its cellular localization but also promotes its catalytic activity and its interaction with XRCC1. These findings indicate that CHK2 exerts a multifaceted impact on PARP1 in response to oxidative stress to facilitate DNA repair and to maintain cell survival.