Lu3+ deficient Lu3−xAl5O12:Ce ceramics were prepared by solid state reaction method. Lu3−xAl5O12:Ce ceramics displayed roughly ∼4 times higher radioluminescence than LuAG:Ce single crystals. Light yield of Lu3–1% Al5O12:Ce at 1 μs shaping time is ∼18,000 ph/MeV and fast decay time ∼60 ns. LuAl antisite defects were suppressed effectively in Lu3−xAl5O12:Ce ceramics. Al-rich second phase impurities were also observed in Lu3−xAl5O12:Ce ceramics.