Various alumina powders were prepared by the complexing agent-assisted sol-gel method and the influence of the complexing agents on the thermostability of alumina-supported palladium and platinum catalysts and on their oxidation of carbon monoxide and methane was investigated. Three alumina-supported palladium catalysts were prepared by an impregnation method. The highest carbon monoxide and methane conversion efficiencies were obtained with a Pd/MPD (2-methylpentane-2,4-diol)-alumina catalyst followed by a Pd/IPA (isopropyl alcohol)-alumina and Pd/commercial alumina catalysts. Two alumina-supported platinum catalysts were prepared, one from a commercial alumina and the other was obtained from aluminium isopropoxide using MPD. The platinum catalyst supported on MPD-alumina showed higher carbon monoxide and methane conversion efficiencies than the platinum catalyst supported on the commercial alumina. It was found that the sol-gel method using MPD as a complexing agent improves the thermostability of alumina-supported palladium and platinum catalysts.