Well-aligned hierarchical nanoarrays containing ZnO core and layered double hydroxide (LDH) nanoplatelets shell have been synthesized via a facile electrosynthesis method. The resulting ZnO@CoNi-LDH core-shell nanoarray exhibits promising behavior in photoelectrochemical water splitting, giving rise to a largely enhanced photocurrent density as well as stability; much superior to those of ZnO-based photoelectrodes. This is attributed to the successful integration of photogenerated electron-hole separation originating from the ZnO core and the excellent electrocatalytic activity of LDH shell. This work provides a facile and cost-effective strategy for the fabrication of multifunctional nanoarrays with a hierarchical structure, which can be potentially used in energy storage and conversion devices.