<p>CdS photocatalysts have attracted extensive attention in the area of photocatalytic hydrogen generation, yet their limited light absorption and charge transfer efficiencies still restrict their photocatalytic performance. In this study, NiS was grown on CdS to synthesize xNiS/CdS composites via a hydrothermal method and was used for photocatalytic hydrogen evolution. The introduction of NiS increased the light absorption intensity and broadened the light absorption range in the visible light region. In addition, a close contact interface formed between NiS and CdS, which accelerated the transfer and separation of photogenerated electrons and holes. Furthermore, NiS acts as the electron aggregation center and active site for photocatalytic hydrogen evolution. Therefore, the photocatalytic performance of the xNiS/CdS composites was greatly enhanced. Among the xNiS/CdS composites, the 0.5NiS/CdS composite exhibited the optimal photocatalytic hydrogen evolution rate of 36.75 mmol·h^− 1·g^− 1, which was 7.84 times greater than that of CdS. A possible mechanism of photocatalytic H₂ production over xNiS/CdS is also proposed. This work provides new inspiration for the rational design of high-efficiency cocatalyst/CdS composites.</p> Graphical Abstract <p></p>