ZnS and iron oxide nanoparticles were first synthesized via precipitation and hydrothermal methods respectively. Fe3O4/ZnS nano-composites were then prepared using precipitation method. The prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. Vibrating sample magnetometer (VSM) was used to study the magnetic property of the products. The photo-catalytic behaviour of Fe3O4/ZnS nanocomposites was evaluated using the degradation of three azo-dyes under ultraviolet light irradiation. The results illustrate super paramagnetic and ferromagnetic behaviour of Fe3O4 nanoparticles. The photo catalytic behaviour of Fe 3O4/ZnS nano-composites was evaluated using the degradation of three various azo dyes under ultraviolet light irradiation. The results show that, the prepared nano-composites are applicable for magnetic and photo catalytic performance.