Hand-foot syndrome (HFS) is a widely recognized dose-limiting cutaneous toxicity effect of fluoropyrimidine chemotherapy agents that impairs clinical benefits and treatment outcomes. Even though the cause and pathophysiology of HFS are relatively widely reported, how the toxicity of fluoropyrimidine translates into persistent inflammation has not been studied. Additionally, prevention and treatment strategies for HFS based on its mechanistic occurrence and development are scarce. In our study, we demonstrated that cGAS-STING signaling pathway-mediated cellular senescence played a critical role in the inflammatory reaction and provided a therapeutic solution for HFS. Mechanistically, DNA damage, as the primary cytotoxic cause, in keratinocytes induces cell cycle arrest, activates the cGAS-STING signaling pathway, and subsequently mediates cellular senescence, ultimately fueling a robust secondary inflammatory response that results in HFS. More importantly, the thymidine prodrug thymidine diacetate was proven to be effective in preventing HFS by compensating for thymidylate deficiency to facilitate the replication and repair of DNA and thus causing the escape from cellular senescence. These data highlight the importance of DNA damage-mediated cellular senescence in the etiology of HFS and provide a potential therapeutic anchor point for fluoropyrimidine-induced HFS.