Electrochemical water splitting is one of the potential approaches for making renewable energy production and storage viable. The oxygen evolution reaction (OER), as a sluggish four-electron electrochemical reaction, has to overcome high overpotential to accomplish overall water splitting. Therefore, developing low-cost and highly active OER catalysts is the key for achieving efficient and economical water electrolysis. In this work, Fe-doped NiMoO4 was synthesized and evaluated as the OER catalyst in alkaline medium. Fe3+ doping helps to regulate the electronic structure of Ni centers in NiMoO4, which consequently promotes the catalytic activity of NiMoO4. The overpotential to reach a current density of 10 mA cm−2 is 299 mV in 1 m KOH for the optimal Ni0.9Fe0.1MoO4, which is 65 mV lower than that for NiMoO4. Further, the catalyst also shows exceptional performance stability during a 2 h chronopotentiometry testing. Moreover, the real catalytically active center of Ni0.9Fe0.1MoO4 is also unraveled based on the ex situ characterizations. These results provide new alternatives for precious-metal-free catalysts for alkaline OER and also expand the Fe-doping-induced synergistic effect towards performance enhancement to new catalyst systems.