Developing efficient and low‐cost photocatalysts and deep investigations on the charge separation and transfer pathways are still two key challenges in achieving practical photocatalytic application. Herein, the NiS‐modified Mo2C/CdS layered nanojunction with cascade 2D coupling interfaces for efficient photocatalytic H2 evolution is constructed. The as‐prepared ternary step‐scheme (S‐scheme) photocatalysts show excellent photocatalytic hydrogen‐evolution performance of 24.03 mmol g−1 h−1, which is 7.83 and 3.83 times higher than that of CdS and CdS/NiS. Surprisingly, it is found that Mo2C can serve as a semiconductor in photocatalytic hydrogen evolution, instead of as a cocatalyst. The charge transfer pathways from Mo2C to CdS are identified via both, in situ irradiation X‐ray photoelectron spectroscopy (XPS) (ISI XPS) and ultraviolet photoelectron spectroscopy (UPS). Notably, this is the first report using Mo2C as a semiconductor for photocatalytic application, which gives full play to the advantages of light‐harvesting and charges separation.