Visible light polymerization of an acrylate in poly(methyl methacrylate) (PMMA) film using a series of dialkylphenacylsulfonium butyltriphenylborate initiators was investigated. When 3,3＇-carbonylbis(7-diethylaminocoumarin) (KCD) was used as a sensitizer, the rates of polymerization (R-p) and the degrees of conversion increased with increasing the reduction potential of the sulfonium cations of the sulfonium berates. They also increased with decreasing lowest unoccupied molecular orbital (LUMO) energy level for the same cations. The photoreaction between the sulfonium berates and KCD was discussed.