A typical reversible addition-fragmentation chain transfer (RAFT) agent, 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN), was used as a single electron transfer-living radical polymerization (SET-LRP) initiator for methyl methacrylate (MMA) polymerization at 25°C. At 1:1 molar ratio of [CPDN] 0 /[Cu(0)] 0 , the apparent rate constants of propagation (k p app ) were 0.037, 0.049, and 0.072 h -1 for [MMA] 0 /[CPDN] 0 of 225/0.2, 225/0.5, and 225/1, respectively. The number-average molecular weight of poly(methyl methacrylate) (PMMA) increased linearly with monomer conversion, and narrow molecular weight distributions (M w /M n <1.50) were found at most cases. At high molar ratio of [CPDN] 0 to [Cu(0)] 0 , such as 1:0.1 in this work, the polymerization was also controllable, whereas it a presented markedly depressed polymerization rate and an obvious induction period. 1 H NMR spectroscope and matrix assisted laser desorption/ionization time-of-flight mass spectrometry confirmed that PMMA chain was end-capped by CPDN species with high fidelity. The tacticity of PMMA from 1 H NMR calculation was about 3.15% isotactic (mm), 29.65% atactic (mr) and 67.20% syndiotactic (rr) triads, consistent with the tacticity distribution for traditional radical polymerizations. Chain extension reactions substantiated further that the obtained PMMA from CPDN mediated SET-LRP was living, and can be reactivated for chain extension reaction. This work demonstrates that a typical RAFT agent can act as a SET-LRP initiator as well as an atom transfer radical polymerization initiator. Furthermore, these results also suggested that the single electron transfer initiation-reversible addition-fragmentation chain transfer control (SET-RAFT) invented by Dhamodharan may not be RAFT at all, but rather SET-LRP initiated by a RAFT reagent, or a combination of SET-LRP and RAFT. Analogously, the exact polymerization process in this work may also proceed in two manners, a fully SET-LRP process and a combination of SET-LRP/RAFT process, which is needed to clarify in the future.