Sub-10 nm CeO2 particles were highly dispersed on Hollandite-type manganese oxide (HMO) to give a CeOx/HMO catalyst, which showed obviously higher activity than HMO and CeO2 alone in CO oxidation and selective catalytic reduction of NO by NH3. A combination of various characterization data with the catalytic tests revealed that the enhanced catalytic activity results from the strong interaction between CeO2 and HMO to activate the transfer of electron, the improved redox ability of surface oxygen due to an increased electron density, and the presence of more surface active oxygen species.