Ternary boron carbonitride (BCN) thin films were prepared by radio frequency reactive sputtering method from a hexagonal (h-) BN target in an Ar-CH4 discharge. The films with different C contents were obtained by varying the CH, partial pressure. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results suggest that the material is not a simple mixture of h-BN and graphite. The samples deposited under the optimum conditions are polycrystalline BC2N. With increasing CH, partial pressure, more B atoms prefer to combine with C atoms. The temperature dependent conductivity of the films deposited at 10% CH4 partial pressure follows the Arrhenius relation; the corresponding activation energy is approximately 0.8 eV.