Ce3 /Er3 /Bi3 triply-doped yttrium aluminum garnet (YAG) is synthesized using co-precipitation method. The Bi3 concentration-dependent near-infrared (NIR) emission behavior is systemically investigated. The NIR emission of Er3 ions at 1531 nm is enhanced threefold by the addition of 7 mol% Bi3 . Bi3 doping results in the formation of exciton in YAG and the variation in the local environment of the doped rare-earth ions. The enhancement in NIR luminescence is ascribed to the combined effects of the sensitization of exciton!Ce3 !Er3 and the Bi3 doping-induced adjustment of the local environment for Ce3 and Er3 ions.