A novel reversible addition-fragmentation chain transfer polymerization (RAFT) of methyl methacrylate (MMA) in the presence of oxygen was carried out for the first time without added chemical initiators. The polymerization was mediated by 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) or cumyl dithionaphthalenoate (CDN) as RAFT agent. The polymerization demonstrated the features of a living/controlled radical polymerization. The polymerization rate increased with oxygen concentration. Polymers with molecular weight M-n up to 520,000 g/mol, polydispersity M-W/M-n similar to 1.46 and RAFT efficiency M-n,M-th/M-n.GPC similar to 1.026 in the case of CPDN and M-n similar to 331,500 g/mol, M-w/M-n similar to 1.35, and M-n,M-th/M-n,M-GPC similar to 1.137 in the case of CDN were obtained. The possible mechanism of the thermal-initiated RAFT polymerization of MMA in the presence of oxygen was discussed.