Developing highly efficient and low-cost electrocatalysts with robust stability for hydrogen evolution reaction (HER) is a significant but challenging work for energy conversion and storage in recent years. In the present work, in situ carbon-decorated Cu3P particles (Cu3P@C) were facially synthesized by a one-pot rapid reaction with the precursors of copper acetylacetonate [Cu(acac)2] and triphenylphosphine (PPh3) at 425 °C for 1 h via a vacuum encapsulation technique. Compared with pure Cu3P particles, the Cu3P@C hybrid catalyst exhibits an enhanced electrocatalytic water-splitting performance for hydrogen evolution with excellent stability. The investigation shows that the hybridization with carbon efficiently facilities the charge transport for the electrochemical reaction. Such results of our study make the present Cu3P@C-based hybrid a promising catalyst for practical applications toward energy conversion and pave way for designing and fast fabricating in situ carbon-decorated HER catalysts from the organometallic precursors.