Pt catalysts supported on mixed CeO2-Al2O3 carriers with different CeO2 loadings (2-50wt.%) were prepared by the sol-gel method. Several techniques such as N2 physisorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) were applied to characterize the physicochemical properties of the catalysts. The temperature-programmed reduction plots indicated that the reduction of the corresponding oxygen species becomes difficult in the samples with high cerium contents due to the fact that reduction of the oxygen from the lattice requires more energy, i.e., greater temperature. The catalysts were tested on the methane oxidation reaction. The results of the tests of Pt/CeO2-Al2O3 catalysts showed a suppression of the activity when the content of CeO2 was increased, although Pt catalyst with 50 wt.% of CeO2 exhibited the highest specific activity.