Ni-C composite films were prepared by codeposition using a combined technique of plasma CVD and ion beam sput-tering deposition. The structure of these films was characterized by in-situ energy-dispersive X-ray diffraction (EDXRD), transmission electron microscopy (TEM) and Raman spectroscopy. It was found that a nickel carbide phase, Ni3C (hcp), formed as very fine crystallites over a wide temperature range when Ni-C films were deposited at low HC4 flow rates. The thermal stability of this nonequilibrium carbide Ni3C was also studied. As a result, the Ni3C carbide was found to decompose into nickel and graphite at around 400°C. With high HC4 flow rates (> 0.2 sccm), the structure of the Ni-C films became amorphous. The formation behavior of the carbide and amorphous Ni-C phases are discussed in relation to the electrical resistivity of the films.