CuAlSe 2 :Er 3 + single crystals were grown by the chemical transport reaction method. The single crystal crystallized in the chalcopyrite structure. The optical energy gap at 10 K was found to be 2.65 eV. The sharp impurity optical absorption peaks due to Er 3 + ion were observed at 544 nm, 657 nm, 980 nm, 990 nm, 1006 nm, 1014 nm and 1544 nm. The sharp photoluminescence peaks due to Er 3 + ion observed at 544 nm, 654 nm, 661 nm and 667 nm, and the broad photoluminescence peak due to a donor-acceptor pair recombination was observed at 674 nm.