In this work, the graphene oxide (GO) sheets were synthesized by modified Hummers and Offeman's method. The GO was mixed with ZnSe that was prepared using various amounts of N2H4 at a ratio of (0.25-2):1 to form precursors. The ZnSe/graphene nanocomposites were synthesized under hydrothermal conditions (180 degrees C; 12 h) from the previous precursor. Obtained ZnSe/graphene photocatalysts were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-vis diffuse reflection spectroscopy, transmission electron microscope, scanning electron microscope, Raman spectra and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity under visible light is evaluated in methylene blue (MB) dye degradation reaction in aqueous phase. The results show that the formation of ZnSe/graphene nanocomposite is depend on ratio of the addition of GO to the amount of ZnSe-N2H4. The optimum degradation efficiency of the ZnSe/graphene nanocomposites on MB increases with increasing the ratio of the addition of GO to the amount of ZnSe-N2H4. When the amount of N2H4 increased from 5 ml to 7 ml, the ratio of the addition of GO to the amount of ZnSe-N2H4 increased from 1 to 1.25. (C) 2015 Elsevier B.V. All rights reserved.