Nanocrystalline nickel doped ZnS (ZnS:Ni) thin films were deposited by chemical bath deposition method. The effect of Ni doping on structural, photoluminescence, and optical properties of the ZnS:Ni films was studied. Structural analysis using X-ray diffraction revealed that the films are polycrystalline in nature with a cubic structure. The fluorescence (FL) spectra of the ZnS:Ni films showed two characteristic bands, one broad band centered at 430 and another narrow band at 523 nm. UV–vis transmission data showed that the films were transparent in the visible region. Also, using these data, the absorption coefficients, the optical band gap, the extinction coefficients, the refractive index, the real and imaginary parts of the dielectric constants, and the dissipation factor were calculated.