Cryptochromes (CRYs) act as blue-light photoreceptors that regulate development and circadian rhythms in plants and animals and as navigating magnetoreceptors in migratory birds. DNA double-strand breaks (DSBs) are the most serious type of DNA damage and threaten genome stability in all organisms. Although CRYs have been shown to respond to DNA damage, whether and how they participate in DSB repair is not well understood. Here we report that Arabidopsis CRYs promote the repair of DSBs through direct interactions with ADA2b and SMC5 in a blue-light-dependent manner to enhance their interaction. Mutations in CRYs and in ADA2b lead to similar enhanced DNA damage accumulation. In response to DNA damage, CRYs are localized at DSBs, and the recruitment of SMC5 to DSBs is dependent on CRYs. These results suggest that CRY-enhanced ADA2b-SMC5 interaction promotes ADA2b-mediated recruitment of SMC5 to DSBs, leading to DSB repair.