Developing low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) has stimulated extensive interest. Molybdenum carbide materials have been proposed as promising alternatives to noble platinum-based catalysts due to their earth abundance and tunable physicochemical characteristics. Here, we report Mo2C@NC/Mo2C hollow microspheres composed of a β-Mo2C core and small β-Mo2C particles embedded within a nitrogen-doped carbon shell and prepared using guanosine and hexaammonium molybdate as precursors via a hydrothermal self-assembly process, which results in outstanding catalytic activity and fast kinetics in hydrogen evolution in both acidic and alkaline solutions. The significant activity improvement of Mo2C@NC/Mo2C can be attributed to the large ratio of exposed active sites and abundant interfacial structures. This work provides a new template-free strategy for the design of a highly active Mo2C@NC/Mo2C hollow microsphere HER catalyst.