In this study, a novel three dimensional (3D) ZnO/Cu₂O nanowire (NW) photocathode material with highly efficient photoelectrocatalytic performance was prepared on a copper substrate using simple, cost-effective wet chemical oxidation and hydrothermal growth methods. FE-SEM, TEM, XRD and XPS were used to investigate the 3D ZnO/Cu₂O NWs, revealing the formation of the high density orientated Cu₂O NW cores and ZnO NW shells. Compared with the pure Cu₂O NWs, the 3D ZnO/Cu₂O NWs showed a larger photocurrent (−4.55 mA cm⁻²) and better stability under AM 1.5G illumination (100 mW cm⁻²). In light of the high effective surface area and the ability to facilitate good electron transportation, this unique nanostructure will be favorable for efficient photoelectrocatalytic (PEC) water splitting and organic pollutant degradation.