The exploration of new heterojunction materials is of great significance in reducing the cost of existing noble metal catalysts and thus realizing the large-scale application of electrocatalytic hydrolysis technology. Herein, a novel CoP/CoMoP₂ heterojunction was synthesized and served as a hydrogen evolution reaction (HER) electrocatalyst. The heterojunction has morphology of nanoporous structure, which is conducive to exposing more active sites and facilitating bubbles transport. The charge distribution is optimized by a strong interface interaction between CoP and CoMoP₂. The catalyst’s conductivity and the adsorption properties of the intermediates have both been enhanced. CoP/CoMoP₂ demonstrates excellent HER activity with an overpotential of 93.6 mV at 10 mA·cm⁻², which is competitive with the reported performance of analogous electrocatalysts. This work provides insights into the development of innovative phosphide-based heterojunction electrocatalysts.