Core/shell nanoparticles having distinct attributes of both core and shell have, of late, become attractive candidates for applications involving surface engineering of nanoparticles. In this work, the synthesis of ZnO/ZnS core/shell nanoparticles by wet chemical method is reported, formation of which is confirmed by HRTEM analysis. Characterization of the core/shell nanoparticles was done using absorption spectroscopy and HRTEM. ZnO/ZnS core/shell nanoparticles exhibited higher photocatalytic activity than the already proved good photocatalyst ZnO. This was supported by photocatalytic degradation experiments carried out on an organic dye, methylene blue, under direct sunlight irradiation. The enhancement in the photocatalytic activity is attributed to the increase of the surface reactivity of the as synthesized material, which is confirmed through the blue shift in the UV Visible absorption spectra. This material can be a promising photocatalyst in the field of water purification. Keywords: visible light, photocatalysis, ZnO, ZnO/ZnS Core/Shell, methelyne blue