A series of Sr-substituted lanthanum manganite perovskites, La1-xSrxMnO3 (LSMO, x = 0, 0.1, 0.2, and 0.3), with mesoporous structures were prepared and coated onto a three-dimensional Ni metal foam (MF) as composite catalysts. The catalytic performances of La0.8Sr0.2MnO3/MF and La0.7Sr0.3MnO3/MF were found to be superior to those of La0.9Sr0.1MnO3/MF, LaMnO3/MF, and LaMnO3 powder in terms of catalytic oxidation of carbon monoxide with air. Under the reaction conditions (1.5 vol.% CO and air balance at a weight hourly space velocity of 90,000 hr–1), La0.8Sr0.2MnO3/MF reached 100% catalytic oxidation of CO, which is 27% higher than that of LaMnO3 powder. Sr substitution induced an increase of Mn4+ and adsorbed surface oxygen species (O–, O2–, or O22–), which increased the number of active centers for oxidation and thus enhanced the oxidizing ability of the catalyst. The high activity and excellent stability of La0.8Sr0.2MnO3/MF catalyst can be ascribed to a synergistic effect between the mesoporous structure and the high number of adsorbed oxygen species of the catalyst as well as the interconnected three-dimensional reticular configuration of the nickel metal support, which increases the number of active sites and enhances mass transfer for CO and O2. La0.8Sr0.2MnO3/MF composite can potentially be used in catalytic converters for CO removal of automotive exhaust gases.