Thin films of Copper Phthalocyanine (CuPc) of about 200 nm thicknesses have been deposited by thermal evaporation method on glass substrate at 303 ᵒK and 403 ᵒK substrate temperature (Ts) and under pressure better than10-5 mbar. This study concentrated on the effect of substrate temperature on some physical properties of CuPc thin films such as optical properties within the visible range. Optical characterization has been carried out at room temperature using the absorption spectra, at normal incidence, in range 200-900 nm. Absorption and extinction coefficients of the films so obtained have been evaluated. Both of these have been observed to vary with wavelength. The values of refractive index have been found to increase with increasing substrate temperature whereas decrease in optical band gap energy, for direct allowed transitions, with increasing substrate temperature has been noticed. It was attributed to the increasing of defects a round Grain boundaries and due the phase transition from β –phase to α –phase.