The oxygen evolution reaction (OER) is a promising energy conversion system, which has been studied a lot in recent years. However, owing to the high overpotential and sluggish kinetics of the OER, an efficient electrocatalyst is necessary to lower the overpotential and accelerate the reaction. In this paper, we report a cobalt phosphide (CoP)/carbon dots (CDs) composite as an electrocatalyst for the OER for the first time. A facile two-step method was used to synthesize the CoP/CDs composite and the concentration of CDs in the composite was further regulated. The experimental results show that when the amount of CDs in the composite is 6 mg (28.79 wt%C), the obtained CoP/CDs composite exhibits optimal electrocatalytic activity (with an overpotential of 400 mV in 1 M KOH at a current density of 10 mA cm⁻²) and high stability towards the OER. The good electrocatalytic activity of the composite is attributed to the small size of CoP and CDs and rapid electron transfer of CDs.