The glass‐ceramics (GC) of gadolinium aluminum gallium garnets with the expected composition of Gd 3 Al 3 Ga 2 O 12 :Ce and Gd 3 Al 3 Ga 2 O 12 :Ce,Be (GAGG:Ce and GAGG:Ce,Be, respectively) are fabricated by crystallization from the Gd 2 O 3 –Al 2 O 3 –Ga 2 O 3 –CeO 2 –SiO 2 –BeO (Gd:Ga:Al ratio is close to 3:2:3) glasses. The influence of Be 2+ co‐doping (including doping level) on the luminescent properties of the GAGG is demonstrated. In particular, Be co‐doping results in the suppression of the Ce 3+ ‐related radioluminescence (RL) and as a consequence, the light yield is lowered as well. The conclusion is made that Be 2+ creates effective electron or hole trapping centers.