In this work, different cobalt-based mixed transition metal oxides (MTMOs) were fabricated by hydrothermal process followed by calcination. Doping Co₃O₄ with other transition metals, such as Ni, Cu, and Mn, resulted in a fascinating morphological transformation from quasi-spherical nanoparticles to hierarchical micro/nanostructures. Hollow urchin-like NiCo₂O₄ exhibited a high specific surface area which led to excellent electrochemical performance towards oxygen evolution reaction (OER). It achieved a low overpotential of about 309 mV at 10 mA/cm² current density, which is comparable to other reported electrocatalysts. Cyclic voltammetry (CV) technique revealed the redox processes that occur on the surface of NiCo₂O₄ and supported that Co⁴⁺ could be the active center during electrocatalysis. In general, the excellent electrocatalytic activity, stability, and reversibility of NiCo₂O₄ in alkaline condition suggest its applicability as an OER electrocatalyst.