Abstract Nickel titanate (NiTiO3) and nickel niobate (NiNb2O6), both with a cationic valence and conduction band, were examined for their photoelectrochemical properties. Applied as photoanode in a photoelectrochemical cell for water electrolysis, reduced pellets of these oxides show a photoresponse when irradiated in the optical band gap. The corresponding absorption is due to Ni2+ → Ti4+ and Ni2+ → Nb5+ charge-transfer transitions, respectively. These are situated at lower energy than the O2− → Ti4+ and O2− → Nb5+ charge-transfer transitions. The flatband potentials of both compounds were determined from photocurrent versus applied potential measurements. During reduction both compounds showed superficial decomposition. The effect of this decomposition on the photocurrents is discussed.