In this work, a facile hydrothermal method was used to grow ZnO nanoflowers onto an interdigital patterned fluorine-doped tin oxide (FTO) glass substrate, and the crystal structure and morphology of the sample were investigated. The results showed that a great number of regular ZnO nanoflowers grew onto the substrate. Furthermore, the ZnO nanoflowers were used as photosensitive layers, an ultraviolet (UV) photodetector was achieved, and its UV sensing performance was evaluated in detail. The results indicated that this ZnO nanoflowers UV photodetector exhibited good response to 365 nm UV light. Its responsivity and detectivity were up to 135.5 A/W (5 V) and 1.5´1013 Jones, respectively, and the response speed was rapid (4.96 s). This work explored a new way for achieving the high-performance nanostructured ZnO UV photodetectors.