A study has been conducted on the structural and morphological characterization of a Ce–Zr mixed oxide-supported Mn oxide as well as on its catalytic activity in the oxidation of particulate matter arising from Diesel engines. X-ray powder diffraction analysis (XRD) and FT-IR and FT-Raman spectroscopy evidence that the support is a fluorite-like ceria–zirconia solid solution, whereas the supported phase corresponds to the manganese oxide denoted as bixbyite (α-Mn2O3). Thermal analyses and FT-IR spectra in air at varying temperatures of soot mechanically mixed with the catalyst evidence that the combustion takes place to a total extent in the range 420–720 K, carboxylic species being detected as intermediate compounds. Moreover, the soot oxidation was studied in a flow reactor and was found to be selective to CO2, with CO as by-product in the range 420–620 K. The amount of the generated CO decreases significantly with increasing O2 concentration in the feed.