The room-temperature hardness of single-crystal and dense polycrystalline BaTiO3 was investigated by microindentation. The longer diagonal of the Knoop indenter was oriented either parallel or perpendicular to the poled axis of the material. The hardness of the unpoled sample was isotropic. However, hardnesses in the poled samples were anisotropic, with the highest hardnesses resulting when the longer diagonal was parallel to the poled axis. The hardness anisotropy may be due primarily to residual stresses caused by the piezoelectric coupling effect.