As a new member of the MXene group, 2D Mo2C has attracted considerable interest due to its potential application as electrodes for energy storage and catalysis. The large‐area synthesis of Mo2C film is needed for such applications. Here, the one‐step direct synthesis of 2D Mo2C‐on‐graphene film by molten copper‐catalyzed chemical vapor deposition (CVD) is reported. High‐quality and uniform Mo2C film in the centimeter range can be grown on graphene using a Mo–Cu alloy catalyst. Within the vertical heterostructure, graphene acts as a diffusion barrier to the phase‐segregated Mo and allows nanometer‐thin Mo2C to be grown. Graphene‐templated growth of Mo2C produces well‐faceted, large‐sized single crystals with low defect density, as confirmed by scanning transmission electron microscopy (STEM) measurements. Due to its more efficient graphene‐mediated charge‐transfer kinetics, the as‐grown Mo2C‐on‐graphene heterostructure shows a much lower onset voltage for hydrogen evolution reactions as compared to Mo2C‐only electrodes.