Rationally designed architecture and smart components of catalysts can greatly accelerate the hydrogen evolution reaction in photoelectrochemical water splitting. Herein, hierarchical NiS quantum dots decorated CuO nanowires@ZnFe2O4 nanosheets core/shell nanoarrays were prepared by a viable multi-step synthesis approach. First, CuO nanowire arrays were prepared through the thermal treatment of copper mesh. Then, CuO@ZnO core/shell nanowire arrays were prepared via an impregnation-calcination process. Next, the CuO nanowire arrays with different ZnFe2O4 nanosheet contents were prepared through wet chemical reaction and subsequent thermal treatment. The further NiS quantum dots decoration was realized through a chemical bath deposition. The CuO nanowire arrays covered with ZnFe2O4 porous nanosheets not only offer abundant active sites to react with the electrolyte but also improve visible light utilization. Moreover, the hierarchical nanoarray structure provides a direct electron transport pathway with a graded interface for better charge flow. As a result, remarkably enhanced photo-electrochemical performance and excellent cycling stability were obtained for the CuO@ZnFe2O4 nanoarray photocathodes due to the synergistic effects of ideal components and hierarchical nanoarray structure. Additionally, the further NiS decoration makes CuO@ZnFe2O4 exhibit a significantly enhanced photocathodic current density. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.