A rapid method for the preparation of highly photoactive CuO thin films on fluorine-doped tin oxide (FTO) glass substrates is reported, based on very simple electrodeposition and post annealing steps. Electrodeposition was performed in an aqueous CuSO4 solution at − 1.5 V vs. Ag|AgCl|3 M KCl for 2 min and the subsequent post-annealing was conducted at 500 °C in air for just 1 min. The electrodes were characterised by SEM, XRD and photo-electrochemical measurements. The CuO thin films exhibited an excellent photocurrent density of 2.1 mA cm− 2 at − 0.6 V vs. Ag|AgCl|3 M KCl in aqueous 1.0 M NaOH which is the highest reported value for a CuO electrode to date.