Photoelectrochemical (PEC) solar water splitting is a promising approach to convert solar energy into sustainable hydrogen fuel using semiconductor electrodes. Owing to their visible light absorption properties, oxynitrides have shown to be attractive photocatalysts for this application. In this study, the influence of the preparation method of CaNbO2N particles on their morphological and optical properties, and thereby their PEC performance, is investigated. The best performing CaNbO2N photoanode is produced by ammonolysis of Nb-enriched calcium niobium oxide.