Cellular senescence is a complex stress response characterized by permanent loss of proliferative capacity and is implicated in age-related disorders. Although the transcriptional activity of p53 (encoded by ) is known to be vital for senescence induction, the downstream effector genes critical for senescence remain unsolved. Recently, we have identified the proline dehydrogenase gene () to be upregulated specifically in senescent cells in a p53-dependent manner, and the functional relevance of this to senescence is yet to be defined. Here, we conducted functional analyses to explore the relationship between PRODH and the senescence program. We found that genetic and pharmacological inhibition of PRODH suppressed senescent phenotypes induced by DNA damage. Furthermore, ectopic expression of wild-type PRODH, but not enzymatically inactive forms, induced senescence associated with the increase in reactive oxygen species (ROS) and the accumulation of DNA damage. Treatment with N-acetyl-L-cysteine, a ROS scavenger, prevented senescence induced by PRODH overexpression. These results indicate that PRODH plays a causative role in DNA damage-induced senescence through the enzymatic generation of ROS.