 Hydrogen evolution reaction (HER) plays a vital role in renewable energy conversion for the development of hydrogen-based energy sources. Lately, heterostructures through hybridizing MXenes with two-dimensional materials have been successfully fabricated and attract much attention due to the exceptional performance as electrodes for Li ion storage and electrocatalysts for HER. Herein, we constructed heterostructures of CoNx-graphene (CoNx-G, x = 2 and 4) supported by MXenes (Ti3C2F2 and Ti3C2O2) monolayer as highly active electrocatalysts for HER. The theoretical results show that the CoN2-G/Ti3C2O2 heterostructure exhibits a high performance for HER with an over-potential (Ƞ) of only 0.33 V, and the rate-limiting step is determined to be the initial water dissociation process in alkaline media. The outstanding performance of CoN2-G/Ti3C2O2 is strongly attributed to the interfacial coupling between CoN2-G and the MXene substrate. Our finding demonstrates that the sluggish hydrogen evolution process in alkaline media can be facilitated by taking advantage of the fast charge transfer kinetics and interfacial coupling of MXenes.