Abstract One of the main problems of the oil refinery industries is the presence of various organic compounds as environmental pollutants in their effluents. One of the most efficient methods for treatment of this type of wastewater and degradation of organic pollutant compounds is the photocatalytic method. In this research, in order to improve the photocatalytic performance of ZnWO4 semiconductor under visible light radiation, its heterojunction composite with NiCo2S4 was prepared. The heterojunction nanocomposites were produced by hydrothermal method using ZnWO4 nanorods and NiCo2S4 nanoparticles. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field emission scanning electron microscope (FESEM), and photoluminescence (PL) techniques were used to characterize these nanocomposites. The results showed that the ZnWO4/NiCo2S4 heterojunction nanocomposite containing 20% W/W of NiCo2S4 has the best photocatalytic performance. Also, the obtained results showed that decreasing of the band gap energy, increasing of the absorption of visible light, and reducing of the hole-electron recombination lead to the improved photocatalytic performance, due to the more effective production of oxidizing radicals such as hydroxyl and superoxide.