ZnO/CuInS2 core/shell nanorods array thin film was synthesized on conducting glass substrates for photoelectrochemical water splitting via a simple hydrothermal and cation exchange reaction, using ZnO nanorods array as reactive template. Uniform CuInS2 films were obtained on the surface of ZnO nanorods, based on the ion-by-ion growth mechanism. The optical property of core/shell nanoarray was characterized, and enhanced absorption spectrum was observed. Hydrogen generation efficiency of 3.2% at 0.29 V versus saturated calomel electrode was achieved with synthesized ZnO/CuInS2 core/shell nanoarray electrode due to the improved absorption and appropriate energy gap structure. The synthesized core/shell nanoarray has potential application in photoelectrochemical water splitting. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.