Iron nitride nanoparticles encapsulated in nitrogen-doped carbon bulk is fabricated by a simple costep nitridation of Fe2O3 and carbonization of polyaniline. The microstructure and elemental composition of the materials are analyzed by transmission electron microscope, scanning electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy. The pore size distribution and specific surface area of the materials are identified using nitrogen adsorption and desorption method. The results illustrate that iron nitride nanoparticles with 5–20 nm in size are uniformly dispersed in the carbon bulk. The presence of carbon bulk effectively prevents the agglomeration of iron nitride nanoparticles, making the electrochemical performance of iron nitride nanoparticles/carbon nitride composite nanomaterials superior to that of pure iron nitride nanomaterials. At a current density of 0.5 A g−1, the specific capacitance (257.5 F g−1) of the iron nitride nanoparticles/nitrogen-doped carbon bulk is much higher than that (119.5 F g−1) of pure iron nitride. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim