Thin films of copper tungstate (CuWO4)have been prepared through electrodeposition and tested as the anode material for photoelectrochemical (PEC) water oxidation. We found that hydrogen-treatment over the synthesized CuWO4 at high temperatures led to enhancement in the PEC performance for water oxidation. The origin of this activity enhancement is attributed to the enhanced kinetics of electron-hole pair separation due to the increased carrier concentration induced by oxygen vacancy formation upon hydrogen-treatment. The incorporation of oxygen vacancies also resulted in enhanced light absorbance in the visible light region because they introduce shallow donors as predicted by first-principles calculations. Nevertheless, incident photon to electron conversion efficiency (IPCE) measurements indicate that light absorbed at long wavelength region after hydrogen-treatment is not successfully utilized to oxidize water. This report provides insights on the effect of hydrogen-treatment on the structural, optical, and electronic properties of CuWO4. (C) 2016 The Electrochemical Society. All rights reserved.