The optical and radioluminescent properties as well as the electronic structure of the recently discovered phase (MeNH₃)Cu₂I₃ are reported for the first time. Single crystals of (MeNH₃)Cu₂I₃ were obtained by crystallization from solution and demonstrated photoluminescence and radioluminescence at 100 K. DFT analysis of both the electronic structure and the partial density of states revealed that (MeNH₃)Cu₂I₃ has a direct bandgap.