The development of platinum-free electrocatalyst for hydrogen evolution reaction (HER) is highly essential to the large-scale production and application of water splitting devices. Herein, a novel type of molybdenum diselenide decorated porous carbon fiber (MoSe2-PCF) composite has been reported for HER. Notably, the unique mesoporous structure of electrospun polystyrene (PS) fibers is perfectly duplicated via the in situ self-polymerization of dopamine by using PS fibers as the hard template, while porous carbon fibers are formed after the subsequent thermal annealing of polydopamine-coated PS fibers. Thus obtained porous carbon fibers exhibit largely improved surface area which could provide highly conductive framework for electron transport, being an ideal substrate for the decoration of MoSe2. With maximally exposed active edge sites from the perpendicularly orientated MoSe2 nanosheets, the MoSe2-PCF composite exhibits high catalytic activity toward HER, holding great potentials as highly efficient metal-free electrodes for energy related applications.