Pure and Ni (0.5-2.0%) doped ZnS nanoparticles were prepared by an inexpensive solid state reaction method. The structural, functional, optical, morphological and chemical compositions of the products were characterized by XRD, FT-IR, UV-Vis, PL, SEM with EDX and TEM analyses. The X-ray diffraction results confirmed that the polycrystalline nature with cubic crystal structure of the nanoparticles. Also, using these data, crystallite size, dislocation density, micro-strain, stacking fault and lattice constant were calculated. The functional group associated with the vibration of a molecule was investigated by FTIR spectroscopy. The optical band gap was increased from 3.58 to 3.97 eV with increasing Ni dopant concentrations. The SEM and TEM images depict the nanosized particles with spherical shape morphology. The elemental composition of Ni-ZnS nanoparticles was examined by EDX analysis. The PL emission spectra show an intensity quenching upon Ni doping and exhibit green emission in the visible region. The photocatalytic activity results indicated that the Ni doping enhanced the photocatalytic activity of ZnS. Thus, Ni-ZnS could be effectively used as photocatalyst for degradation of environmental pollutant Methylene Blue dye.