Thin film heterojunctions of p-CuO/n-ZnO are prepared by magnetron sputtering and their electrical properties are investigated without and with external illumination. Radio-frequency (rf) sputtering in reactive oxygen–argon atmosphere is optimized to achieve phase-pure p-CuO thin films with mobilities up to 6.6 cm2 Vs−1 and hole concentrations in the order of 1017 cm−3. Intrinsic ZnO and conducting ZnO:Al are deposited by rf magnetron sputtering to form heterojunctions with CuO in both substrate and superstrate configurations with various Ohmic contacts to p-CuO. Heterojunctions in the substrate configuration do not possess diode properties, while devices in the superstrate configuration show clear rectifying characteristics with a threshold voltage (VTH) of 0.66 V and a forward-to-reverse current ratio of ∼450 at VTH. These junctions exhibit a weak photovoltaic effect under illumination, but reasons for the poor photoresponse are still to be identified.