Cobalt carbide nanoparticles (NPs), as a typical carbide material, have attracted extensive attention in the fields of magnetism and electrochemistry. Herein, we adopted a modified solution route by pyrolysis long-chain amines at high temperatures to obtain Co₂C NPs, in which different forms of Co NPs were used as precursors. The results reveal that no matter what the structure of the precursor and the type of long-chain amine, single-phase Co₂C NPs with good crystallinity are obtained. At the same time, carbonization of hexagonal close packed (hcp) cobalt as the precursor gives the materials high magnetic anisotropy, exhibiting a large coercivity (~ 1,300 Oe) on the nanoscale. In terms of catalytic properties, benefiting from intrinsically high activity of Co₂C NPs, the material demonstrates superior hydrogen evolution reaction (HER) performance, with optimal overpotential as low as 73 mV at the current density of 10 mA·cm⁻². This provides new ideas for the further development of transition metal carbides (TMCs) and the improvement of their magnetic and electrocatalytic properties.