In this Article, we report the effect of postdeposition thermal treatment on reactively cosputtered copper tungstate (CuWO₄) thin films and its impact on photoelectrochemical performances. This study indicates that CuWO₄ films fabricated at 275 °C were amorphous and did not show significant photoresponse in 0.33 M H₃PO₄ electrolyte when irradiated with air mass 1.5_Global simulated illumination. However, a major improvement in photoelectrochemical performance was observed in identical test conditions after a postdeposition treatment performed at 500 °C in pure argon for 8 h. Indeed, a photocurrent density of approximately 400 μA cm^–2 at 1.6 V vs saturated calomel electrode was measured on the annealed CuWO₄ samples. Subsequent X-ray diffraction analysis revealed a clear transformation of as-deposited amorphous thin films into a triclinic CuWO₄ structure after the annealing step. The polycrystalline CuWO₄ films exhibited n-type conductivity, an indirect band gap of 2.25 eV, and a flat-band potential of −0.35 V vs saturated calomel electrode.