Although the generation of hydrogen by electrolysis of water is cheapest from all other available sources but splitting of water still takes place with sluggish kinetics and is a challenging barrier for H₂ production on large scale. Moreover, research work is still in progress to understand the oxygen evolution reaction (OER) and design the catalysts with improved OER performance. Herein, we report synthesis, characterization, and OER performance of copper oxide/copper sulfide (CuO/CuS) heterostructures and its individual components copper oxide (CuO) and copper sulfide (CuS) as low-cost catalysts for water oxidation. CuO/CuS has been demonstrated to be a stable and effective catalyst that initiates the OER at a potential of 1.49 V. (vs. RHE). The CuO/CuS catalyst drives the OER at only 270 mV overpotential and Tafel slope of 67 mV dec⁻¹ with a current density of 10 mA cm⁻² in 1.0 M KOH. CuO/CuS heterostructures outperforms OER performance of previously reported Cu-based catalysts. Long-term stability and performance toward OER are demonstrated by the oxygen evolution at an applied potential of 1.65 V (vs. RHE) over an extended period. This feature brings a favourable, non-noble, highly efficient, and robust OER catalyst.