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.