Rose-petal-shaped MoS2 hierarchical nanostructures were designed and constructed using carbonized electrospun nanofibers as a template, which exhibit highly structure-sensitive properties for the hydrogen evolution reaction (HER). We first synthesized carbon nanofiber (CNF) mats by combining the electrospinning and carbonization processes, and then the CNF mats were used as a substrate for the direct growth of MoS2 nanocrystals via the CVD method. By controlling the MoS2 morphology at the nanoscale, we constructed evolutions in the structures and preferentially exposed more catalytically active edge sites, enabling improved performance for electrochemical catalytic activity. Because of their highly exposed edges and excellent chemical and electrical coupling to the underlying CNFs, MoS2-CNF fiber mats exhibited excellent HER activity with a small overpotential of similar to 0.12 V and a small Tafel slope of 45 mV per decade. Our findings provide a feasible way to design and engineer advanced nanostructures for catalysis, electronic devices, and other potential applications.