The oxygen evolution reaction (OER) is a significant reaction in water splitting and energy conversion. However, high price and sluggish kinetics catalysts prevent commercial applications. Generally, noble metals (e.g., iridium and ruthenium), which are expensive and unstable, have been used as catalysts for OER because of their high electrocatalytic activity. In this study, we report a high-performance OER catalyst with oxygen vacancies comprising NiO/Co3O4 nanohybrids. For OER, the NiO/Co3O4 heterostructure show good electrocatalytic performance with a low overpotential of 330 mV. This is higher than those of NiO, Co3O4, and benchmark IrO2 candidates at current density of 10 mA cm−2. Furthermore, the NiO/Co3O4 nanohybrids show long-term electrochemical stability for 10 h. The present research results show that NiO/Co3O4 heterostructure is an excellent electrocatalyst for OER.