SiO2/SiC core-shell hybrid was prepared by oxidation of silicon carbide fibers. The material was thermally oxidized to observe the oxidation layer on the surface of the silicon carbide. The electrical and thermal properties of the epoxy composites consisting of SiC or SiO2/SiC were investigated. The thermal conductivity of SiO2/SiC-epoxy composites increased with increasing oxidation temperature. The thermal conductivity of the SiO2/SiC-epoxy composite was higher than that of the SiC-epoxy composite. The surface resistance and breakdown strength of the epoxy composite containing SiO2/SiC increased after the thermal oxidation of SiC. The developed SiO2/SiC could be used for electronic packaging applications.