Heterojunction structures improve the intrinsic activity of electrocatalysts by enhancing the charge transfer between the catalyst and the electrode. In this paper, the NiS/FeS₂ heterostructured electrocatalyst is fabricated by a simple sulfidation method using an interface engineering strategy to adjust the surface electron density of the electrocatalyst. As expected, NiS/FeS₂ electrocatalyst exhibits superior activity and durable oxygen evolution reaction (OER) stability, requiring only a low overpotential of 183 mV to achieve a current density of 10 mA·cm⁻² and can be stable for more than 80 h, superior to NiS, FeS₂ electrocatalyst individually, and precious RuO₂. Notably, NiS/FeS₂ is also a good bifunctional electrocatalyst with good overall water splitting performance, and it only requires a voltage 1.56 V to obtain a current density of 10 mA·cm⁻² for more than 12 h. Remarkably, the NiS/FeS₂ hybridization facilitates the formation of coral-like structures, increasing the electrochemical surface area (ECSA) and enhancing the charge transfer efficiency, thus leading to excellent electrocatalytic performance. This work proposes a constructive strategy for designing efficient electrocatalysts based on interface engineering, and lays a foundation for designing a new class of electrocatalysts.