Herein, we reported a facile and readily accessible visible-light-driven photocatalytic protocol to induce oxidative cleavage of C═C bonds to corresponding carbonyls using CsPbBr3 nanocrystals as photocatalysts. This catalytic system was applicable to a wide range of terminal and internal alkenes. Detailed mechanism studies indicated that a single-electron transfer (SET) process was involved in this transformation, wherein the superoxide radical (O2•-) and photogenerated holes played crucial roles. Additionally, DFT calculations revealed that the reaction was initiated by the addition of O2•- to the terminal carbon atom of the C═C bond and completed by releasing one molecular formaldehyde by the formed [2 + 2] intermediate; the latter conversion was a rate-determining process.