A 1.5 J Nd:LuAG ceramic active mirror laser amplifier with a high beam quality is demonstrated in which a 0.8% (atomic fraction) Nd-doped Nd:LuAG ceramic disk with a diameter of 64 mm and a thickness of 5.5 mm is used as a laser gain medium. A maximum single-pass small-signal gain of 2.59 is measured when the pump energy is 11.5 J, with an injected seed energy of 0.4 J; a maximum output energy of 1.5 J is obtained at the repetition rate of 10 Hz. A far-field beam spot 1.25 times the diffraction limit (DL) is achieved by using a stimulated Brillouin scattering phase conjugation mirror (SBS-PCM) for wavefront correction.