Direct　functionalization　of　abundant　C(sp3)-H　bonds　is　highly　attractive.　Photobiocatalysis　offers　promise　for　expanding　enzyme　reactivity　but　has　been　limited　to　the　use　of　preactivated　radical　precursors.　Key　challenges　for　C(sp3)-H　bond　activation　include　the　lack　of　robust　activation　modes　for　the　inert　bonds　under　biocatalytic　conditions　and　controlling　the　reactivity　and　stereochemistry　of　prochiral　radicals.　Here　we　report　a　triple　activation　strategy　enabling　photobiocatalytic　C(sp3)-H　bond　acylation　with　aldehydes.　By　combining　hydrogen-atom　transfer　for　prochiral　radical　formation,　organic-dye-modulated　single-electron　transfer　and　an　engineered　thiamine-dependent　enzyme,　we　describe　a　radical　acyl　transferase　for　functionalizing　C(sp3)-H　bonds.　This　robust　radical　enzymatic　system　achieves　benzylic　C(sp3)-H　and　aldehyde　C(sp2)-H　oxidative　coupling　in　an　enantioselective　manner　(up　to　97%　e.e.).