Effect of photo-accelerator (PA) on the mechanical properties of light-activated polymeric dental restorative composites (PDRC) was investigated. A visible light system was adopted to activate the resin matrix [(2,2'-bis-[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane/triethyleneglycol dimethacrylate, 70/30 wt%] in the PDRC. Silanized barium silicate (75 wt% of PDRC) and camphorquinone (0.5 wt% of the resin matrix) were also used as a filler and photo-initiator, respectively. A variety of aliphatic or aromatic amines were adopted as a PA and their contents were varied from 0.2 to 3.0 wt% of the resin matrix. Effect of PA on the mechanical properties of PDRC was characterized by measuring the diametral tensile strength, flexural strength, and flexural modulus.