Nanocrystalline Fe/Fe₃C composites have been fabricated by an efficient solid-state synthesis route. In this reaction process, we choose the organic compound melamine as the carbon source and hydrothermally prepared nanocrystalline Fe/Fe₃O₄ composite as metal precursor. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and vibrating sample magnetometry have been used to characterize the composites. The experimental results show that changing reaction temperature, reaction time and the amount of melamine allows control over the composition of Fe/Fe₃C composites, particle morphology and magnetic properties. The possible formation mechanisms of as-prepared nanostructures with different morphologies are discussed briefly. Magnetization measurements indicate that the composites display ferromagnetic properties at room temperature.