A series of high-quality N-doped graphene (N-graphene)/Fe₃O₄ nanocomposites were readily obtained by a simple one-pot hydrothermal method under mild conditions. The as-prepared N-graphene/Fe₃O₄ hybrids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and thermogravimetric analysis (TGA). The experimental results demonstrated that ferromagnetic Fe₃O₄ nanocrystals (NCs) of sub-9 nm are facilely achieved and densely anchored onto the surface of N-graphene nanosheets. As an electrode material for electrochemical capacitors, the electrochemical properties of N-graphene/Fe₃O₄ nanocomposites were tested, and it was interesting to find that the combination of N-graphene nanosheets with Fe₃O₄ NCs showed much higher specific capacitance than that of either pure N-graphene or pure Fe₃O₄ NCs, making them a promising electrode material for supercapacitors. Furthermore, the N-graphene hybrids also showed stable cycling performance along with 95% specific capacitance retained after 1000 cycle tests.