Hydrogen holds great promise in the pursuit of decarbonizing energy systems. One of the key processes in hydrogen production is the hydrogen evolution reaction (HER), which relies on efficient catalysts. Cobalt sulfide (CoS) has attracted significant attention owing to its exceptional catalytic activity for HER. However, it suffers from low intrinsic catalytic activity. In this study, we aimed to enhance the catalytic activity of CoS materials for HER by fabricating cobalt sulfide on Ni foam (NF@CoS) through hydrothermal synthesis and applying surface modification techniques such as plasma treatment. Various gases, including H, O, N, and Ar, were used to subject CoS to plasma treatment. The results demonstrated that the optimal sample, named AP-NF@CoS, obtained through Ar plasma treatment, exhibited the lowest overpotential of 133 mV at a current density of 50 mA cm. Furthermore, the AP-NF@CoS sample displayed excellent performance, with a Tafel slope of 129 mV dec. These findings indicate that plasma treatment on NF@CoS is an effective method for producing high-performance electrocatalysts for the HER.