Transition-metal-based layered double hydroxides (TM LDHs) have emerged as highly efficient water oxidation catalysts. They are promising and have the potential to replace the rare and expensive precious metal-based ones such as RuO2 and IrO2, which have been well established. In this perspective, we will summarize the current development of TM LDHs as oxygen evolution reaction (OER) catalysts toward electrochemical water splitting. Particular emphasis will be placed on the roles of the transition-metal cations and the effects of their combination on their catalytic performance for the OER. It is hoped that this perspective will provide fundamental guidelines for future researches in this booming area.