Cobalt carbide nanoparticles including Co2C and Co3C attract great interest as magnetic materials due to their large coercivities and high saturation magnetization. However, it’s hard to obtain the pure phase Co2C with good magnetic properties. A facile method to synthesize the pure phase ferromagnetic Co2C via a one-step polyol reduction process is developed. The crystal structure, morphology ... [Show full abstract] and composition of Co2C nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Saturation magnetization and coercivity of the Co2C measured at 300K are 13.6 emu g⁻¹ and 0.58 kOe, respectively. The carbon contents, particle size and morphology of the Co2C are responsible for the large magnetization and high coercivity. This work will provide a strategy to synthesize pure metal carbides for applications in magnetic fields or energy materials.