In this research, Cu-doped ZnSe nanoparticles were prepared by microwave-assisted hydrothermal method at constant pH of 11.2. The XRD patterns certified formation of the nanoparticles with the size approximately 2 nm. In addition, FESEM and TEM images confirmed the formation of round-shape particles. The results of photocatalytic tests indicated that the sample containing 2.25% of Cu exhibits the highest rate constant value (0.0255 min-1) and the maximum efficiency (75.7% after 60 minutes) for degrading the direct blue 71 azo dye, introducing it as the prime candidate for photocatalytic applications.