Sintered SiC substrate was coated with HfO2 by a sol-gel process using Hf(OEt)4, diethanol-amine, and ethanol. The HfO 2-coated SiC specimen was oxidized isothermally in high purity Ar gas flow at 1873 K for 36 ks and the weight change was monitored by an electro-microbalance. The weight of the un-coated SiC specimen decreased significantly due to the active oxidation, while the weight losses of HfO 2-coated SiC specimens after the isothermal oxidation for 36 ks were smaller than that of un-coated specimen. TEM image of HfO2-coated SiC specimen after oxidation depicted that thick SiO2 layer (∼800 nm) with a small amount of Hf elements formed on the surface of the specimen. XRD analysis indicated that HfC formed during the isothermal oxidation of HfO2-coated SiC specimen.