Molybdenum (Mo) carbide-based materials are considered to be promising electrocatalysts for the hydrogen evolution reaction (HER). One dimensional nanostructured Mo carbides are advantageous in providing abundant accessible catalytically active sites and facilitating electron and mass transfer. In this work, N-doped carbon nanofibers decorated with numerous ultrafine Mo2C nanoparticles with a size of less than 5 nm have been fabricated by an electrospinning-assisted synthetic strategy. The optimized sample Mo2C@CNFs-3 exhibits excellent catalytic performance for the HER in both acidic and alkaline media, which makes it one of the best electrocatalysts among the recently reported Mo carbide-based electrocatalysts. Additionally, other mono- or even bi-transition metal carbides with a nanofibrous structure have been prepared by the same strategy, thereby expanding opportunities in various catalytic applications.