We report the electrical and optical properties of ZnO/ZnS core/shell nanowire (NW) devices. The spatial separation of charge carriers due to their type II band structure together with passivation effect on ZnO/ZnS core/shell NWs not only enhanced their charge carrier transport characteristics by confining the electrons and reducing surface states in the ZnO channel but also increased the photocurrent under ultraviolet (UV) illumination by reducing the recombination probability of the photogenerated charge carriers. Here the efficacy of the type-II band structure and the passivation effect are demonstrated by showing the enhanced subthreshold swing (150 mV/decade) and mobility (17.2 cm²/(V s)) of the electrical properties, as well as the high responsivity (4.4 × 10⁶ A/W) in the optical properties of the ZnO/ZnS core/shell NWs, compared with the subthreshold swing (464 mV/decade), mobility (8.9 cm²/(V s)) and responsivity (2.5 × 10⁶ A/W) of ZnO NWs.