The structural and optical properties of copper oxide thin film have been investigated using various characterization techniques. These thin films have potential applications in thin film solar cells that utilize the visible and UV regions of the solar spectrum. Copper oxide thin films are deposited using RF magnetron sputtering equipped with mass flow controllers. The samples are in-situ annealed post deposition at 300 °C in oxygen ambient to improve the structural properties. Such annealed sample exhibit narrow (002) and (020) CuO peaks and (111)Cu2O peak. X-ray diffraction results confirm the formation of polycrystalline CuO and mixed phases of CuO -Cu2O. A Lowest FWHM of 0.00079 rad has been observed in the XRD spectrum, indicative of excellent crystalline quality of copper oxide thin films. UV–Visible Spectroscopy measurement performed on the copper oxide samples, showed a wide range of absorption edge ranging from 3.9 eV to 3.75 eV for various deposition temperatures ranging from 50 °C to 150 °C. The annealing effect at high temperature for longer duration results in the formation of CuO phase as confirmed by absorption edge at 2.85 eV and the presence of (002) and (020) CuO XRD peaks. In-situ annealing also showed the onset of Urbach effect due to the transitions at tail states and band to tail states.