Mn2+-doped ZnS nanoparticles were prepared by chemical arrested precipitation method. The samples were heated at 300, 500, 700 and 900°C. The average particle size was determined from the X-ray line broadening. Samples were characterized by XRD, FTIR and UV. The composition was verified by EDAX spectrum. The hexagonal structure of the sample was identified. The size of the particles increased as the annealing temperature was increased. The crystallite size varied from 5 nm to 34 nm as the calcination temperature increased. At around 700°C, ZnS is converted into ZnO phase due to oxidation. The emission peak of the sample is observed at 300 nm resulting in blue emission. The solid state theory based on the delocalized electron and hole within the confined volume can explain the blue-shifted optical absorption spectra. UV-VIS spectro-photometric measurement shows an indirect allowed band gap of 3.65 eV.