We studied rapid densification and homogenization of sintered yttrium aluminum garnet (YAG) ceramics via sintering followed by femtosecond pulse laser (800 nm) irradiation. We formed localized, high-density microstructures within a YAG ceramic matrix. The laser irradiated regions were characterized using scanning electron microscopy, elemental mapping, and x-ray diffraction. Our results show that phase separation of YAG into and can be obtained in situ within stoichiometric YAG. With an optimum laser power and processing conditions, this process can be used for producing dense YAG ceramics.