Benefiting from merits such as high electrical conductivity, non-toxicity and low cost, copper sulfides are considered one of the most promising electrocatalysts for both of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities in KOH electrolytes. Nonetheless, this electrocatalyst has indicated high overpotential in previous studies. To address this problem, this work introduces a phosphorus-doped copper sulfide on nickel foam (CuS@NF) as the electrocatalyst with spherical morphology, synthesized through a simple two-step process, for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Electrochemical tests showed that P-doped CuS@NF exhibited excellent catalytic performance with overpotentials of 170 mV for OER and 255 mV for HER at a current density of 50 mA/cm². In comparison, the undoped CuS@NF catalyst required overpotentials of 310 mV for OER and 347 mV for HER under the same conditions. Furthermore, P-doped CuS@NF demonstrated improved stability over its undoped counterpart. Density functional theory (DFT) calculations confirmed that phosphorus doping significantly lowered the overpotentials, especially for the OER, highlighting the enhanced activity of this non-noble metal catalyst.