Monodispersed yttrium aluminum garnet (YAG) powders have been synthesized via homogeneous precipitation method from the mixed solutions of yttrium nitrate, aluminum nitrate, and ammonium aluminum sulfate using urea as the precipitant. The molar ratio of aluminum nitrate to ammonium aluminum sulfate has a significant effect on morphology and particle size of the precursor powders. It was found that spherical precursor particles can be obtained when the ratio is 1:1. During the homogeneous precipitation process, aluminum ions precipitate first and form monodispered spherical powders, and then yttrium ions precipitate onto the surface of the existing spheres. Monodispersed spherical YAG particles with 500 nm in diameter were obtained by calcining the precursor powder at 1100°C for 5 h. The so-prepared monodispersed spherical Nd:YAG powders have good sinterability, and can be sintered into transparent ceramics by vacuum sintering at 1650°C for 3.5 h.