Thin films of ZnO have been prepared on glass substrates at different thicknesses by spray pyrolysis technique using 0.2M aqueous solution of zinc acetate. X-ray diffraction reveals that the films are polycrystalline in nature having hexagonal wurtzite type crystal structure. The resistivity at room temperature is of the order 10 −2 Ωcm and decreased as the temperature increased. Films are highly transparent in the visible region. The dependence of the refractive index, n, and extinction coefficient, k, on the wavelength for a sprayed film is also reported. Optical bandgap, E g , has been reported for the films. A shift from E g =3.21eV to 3.31eV has been observed for deposited films.