The optical properties of cobalt oxide samples prepared by spray pyrolysis technique on glass substrates with different film thicknesses have been studied. The structural characteristics of the samples were investigated using X-ray diffraction. The optical properties of the prepared films were studied by transmittance and reflectance measurements, and the integrated transmittance (TVIS, and TNIR) and absorptance (AVIS and ANIR) in VIS and NIR regions was calculated and found to be affected by film thickness. The dependence of absorption coefficient on wave length was also reported. The energy gap was calculated and two energies have been observed at 2.15 and 1.5 eV suggesting that the deposited films are semi-conducting with allowed direct transitions.