The catalytic activity of nanosize gold catalysts supported on MnO2-TiO2 and prepared by deposition-precipitation method has been investigated for preferential oxidation of carbon monoxide in H2 stream. The catalysts were characterized by inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, nitrogen sorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. The influence of pH in the preparation process and the amount of MnO2 loading on the catalytic properties of the Au/MnO2-TiO2 catalysts were also studied. Fine dispersion of gold nanoparticles on all the supports was obtained. Especially, Au/MnO2-TiO2 with MnO2/TiO2 mol ratio of 2:98, showed a mean Au particle size of 2.37 nm. The nanosized support constrained the size of gold. The addition of MnO2 on Au/TiO2 catalyst improved the selectivity of CO oxidation without sacrificing CO conversion in hydrogen stream between 50 and 100 °C. This could be attributed to the interactions of gold metal with MnO2-TiO2 support and the optimum combination of metallic and electron-deficient gold on the catalyst surface.