In the present work, PVP encapsulated ZnS:Ni nanoparticles were prepared through modified chemical precipitation method using oxalic acid precursor. The structural and optical properties of the prepared samples were characterized using X-ray diffraction (XRD) studies and UV–Vis-NIR Spectrophotometer. Morphological and chemical properties were studied carried out using Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis of X-rays (EDAX). XRD pattern analysis confirms the zinc blende structure of pure ZnS and PVP encapsulated Ni doped ZnS nanoparticles with the crystallite size of 10 nm. The optical band gap has been found to be in the range 4.2- 3.9 eV. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. The degradation of methyl orange (MO) under visible light irradiation was carried out to study the photocatalytic activity of the prepared samples. It was found that the sample 0.5% Ni substituted ZnS exhibited the higher photocatalytic activity due to higher initial saturation value under UV irradiation for 15 min.