5% Fe and Mn-doped nano ZnS (Zn0.95A0.05S, A=Fe or Mn) was prepared using the thermolysis technique. The effect of Fe and Mn doping on the lattice parameter, crystallite size, and lattice microstrain was examined applying Rietveld refinement. The analysis showed the incorporation of Fe and Mn substitutionally for Zn ions; a result confirmed by Fourier transforms infrared spectroscopy spectra from the shift in the vibration bands upon doping. The energy of ZnS band gap was reduced by doping, giving ZnS new applications. The different defects inside the different samples were investigated using photoluminescence spectroscopy. The effect of Fe/ Mn doping and incorporation of atmospheric oxygen on the bandgap characteristics, the absorption, optical conductivity, refractive index and the extinction coefficient, reflectance, the real and imaginary parts of the dielectric constant were explored using density function theory calculation (DFT).