Carbon-infiltrated iron ores were prepared from a coal-tar solution and selected calcined iron sources (i.e., goethite (FeOOH) ore, high-grade hematite ore, and Fe2O3 reagent grain). A several hundred micrometer thick carbon layer was deposited on the surface of all iron sources. Because the tar solution successfully penetrated into its nanopores, only goethite ore possessed a significant amount of carbon in its interior nanopores. The carbon-infiltrated ores were heated rapidly in an oxygen atmosphere in the combustion synthesis experiments. Carbon combustion occurred at the ore surface, with the ore temperature increasing suddenly during the experiments. Fast reduction to metallic iron was observed only in the carbon-infiltrated goethite ore, regardless of the oxygen atmosphere. Close contact between the goethite ore and the carbon in its nanoporous interior facilitated the fast reduction. The apparent reduction reaction of goethite ore is akin to a direct reduction reaction (i.e., FeO x + C → FeO x-1 + CO).