Hydrogen is considered a future energy carrier that could improve energy storage of intermittent solar/wind power to solve energy and environmental problems. Based on such demand, development of electrocatalysts for hydrogen generation has been actively pursued. Although Pt is the most efficient catalyst for the hydrogen evolution reaction (HER), it has limits for widespread application, mainly its low abundance and high cost. Thus, developing an efficient catalyst from non-precious metals that are abundant and inexpensive remains an important challenge to replacement of Pt. Transition metals have been considered possible candidates to replace Pt-based catalysts. In this review, among the transition metals, we focus on recently developed molybdenum-carbon (Mo-C) hybrid materials as electrocatalysts for HER. In particular, the synthesis strategy for Mo-C hybrid electrocatalysts and the role of various carbon nanocomposites in Mo-C hybrid systems are highlighted.