Transition-metal carbides have been proven to be efficient catalysts for the hydrogen evolution reaction (HER); however, their application as a bifunctional electrocatalyst towards the HER and oxygen evolution reaction (OER) altogether remains a significant challenge. Herein, we report unique heterostructures comprising cobalt-doped molybdenum-carbide (Co-Mo₂C) nanorods encapsulated in nitrogen-doped graphitic carbon shell (NGCS) through one-step pyrolysis of a Co-adenine-MoO₃ hybrid. The as-synthesized Co-Mo₂C@NGCS heterostructures could be directly used as a catalyst for overall water splitting. Low overpotentials of 161 and 360 mV are needed for the HER and OER to reach 10 mA cm^-2, and the corresponding Tafel slopes are just 60 and 54 mV dec^-1, respectively. Theoretical simulations implied that the synergistic effects between the cobalt heteroatoms, NGCS and Mo₂C resulted in the enhanced catalytic performance. Our work not only provides a facile method to construct hybrid electrocatalysts with inexpensive metals, but also gives new insights into the mechanism of the HER and OER in alkaline media.