The ZnWO4/Ag3PO4 nanocomposites synthesized by simple precipitation processes were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra. The results indicated that the ZnWO4 nanorods dispersed well on the surface of Ag3PO4 particles and ball-and-rod structure p-n heterojunctions were successfully fabricated. In subsequent degradation experiments of methyl orange (MO), ZnWO4/Ag3PO4 composites showed the highest photocatalytic activity compared to pure Ag3PO4 and ZnWO4, due to the presence of ZnWO4/Ag3PO4 heterojunctions, which could separate and transfer the electron–hole pairs generated by visible light and enhance the photocatalytic performance of the catalysts. The band gap structure and degradation mechanism of the enhanced photocatalytic materials are also discussed in this article. In conclusion, the ZnWO4/Ag3PO4 composite is a promising and excellent photocatalyst for the degradation of dye wastewater under visible light irradiation.