Electrochemical water splitting is one of the potential commercial techniques to produce clean hydrogen energy because of the high efficiency and environmental friendliness. However, development of low-cost bifunctional electrocatalysts that can replace Pt-based catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is challenging. Herein, Co nanoparticles (NPs) are anchored on MoO₂ nanosheets (Co/MoO₂) by thermal reduction of the CoMoO₄ nanosheet array in Ar/H₂. The uniformly distributed Co NPs improve the electron transfer capability and modulate the surface states of the MoO₂ nanosheets to enhance hydrogen desorption and HER kinetics. Moreover, the Co/MoO₂ composite is beneficial to the interfacial structure and the MoO₂ nanosheets prevent aggregation of Co NPs to improve the intrinsic OER characteristics in the alkaline electrolyte. As a result, the Co/MoO₂ electrocatalyst shows low HER and OER overpotentials of 178 and 318 mV at a current density of 10 mA cm⁻² in 1 M KOH. The electrolytic cell consisting of the bifunctional Co/MoO₂ electrodes shows a small voltage of 1.72 V for a current density of 10 mA cm⁻² in overall water splitting.