This research work is devoted to the study of optical properties of thermally evaporated and laser annealed ZnSe thin films. Thin films of zinc selenide were annealed by a CO2 pulsed laser at different powers (10, 20 and 30 Watt). As shown by X-ray diffraction analysis, all the studied films exhibit cubic zinc blende crystal structure with dominant preferred orientation along the plane (111). Optical transmission spectra, were investigated in the spectral range 300–2500 nm at room temperature. Swanepoel’s envelope method was employed to check the film thicknesses, as well as to evaluate the refractive index, absorption coefficient and the extinction coefficient by using transmission measurements only. Optical energy gap was determined using Tauc plot extrapolation. It was found to be increased from 2.67 to 2.90 eV with increasing the pulsed laser annealing power and it is due to allowed direct transition. Using Wemple-DiDomenico single oscillator model, the dispersion of the refractive index and energy dispersion parameters together with their dependences on the laser annealing power have been studied.