A high entropy spinel oxide (Cr_0.2Mn_0.2Fe_0.2Ni_0.2Zn_0.2)₃O₄ is successfully synthesized via the solvothermal method, and its electrocatalytic properties for the oxygen evolution reaction (OER) are evaluated. The catalyst exhibits a low overpotential of 295 mV at 10 mA cm⁻², with a Tafel slope of 53.7 mV dec⁻¹ as well as promising long-term stability. The attractive performance can be attributed to the increased amount of high valence Ni³⁺ species, together with the improved adsorption ability of oxygenic species on the material surface, due to the contribution of the multi-metallic element doping strategy in high entropy spinel oxide. DFT calculation results prove that the covalency of the metal–oxygen bond is enhanced in the high entropy oxide, which is beneficial for the OER catalysis. The DOS profile analysis and different charge density mapping results further reveal the multi-metal synergistic contribution to the oxygen evolution reaction. This study provides a reference method for the design and development of high-entropy spinel oxides with excellent OER properties.