A set of cordierite Ce-La/SiO2-Al2O3-MgO-ZrO2 catalyst washcoats containing various weight percentages of Ce-La with mesopores of ~ 3 nm was prepared by the co-precipitation/impregnation method. The structural and physicochemical properties of the prepared catalyst washcoats were obtained using complementary techniques such as TGA/DSC, DLS, XRD, FE-SEM, EDS, BET, and TEM. The O2-temperature-programmed desorption (O2-TPD) results were used to study their oxygen properties. As a whole, the presence of high-entropy Ce-La oxides caused the lattice expansion of the cordierite Ce-La/SiO2-Al2O3-MgO-ZrO2 structure. On the other hand, the average particle size, around 3-4 μm, and their distribution for all samples was independent of the amount of Ce-La. The results of TGA-DSC, XRD, and EDS analysis confirmed the presence of Ce-La elements in the cordierite structure and the formation of the oxide phase. The O2-TPD data analysis showed that at a higher weight percentage of Ce-La, the amount of γ-oxygen decreased and the β-oxygen increased, which was very favorable regarding the deep oxidation ability of the catalysts. Finally, the most appropriate weight percentage of Ce-La (12 wt.%), with regard to the surface area, porosity, and oxygen properties, was washcoated in a cordierite honeycomb ceramic monolith; its surface morphology was studied by FE-SEM and compared with the bare monolith. As a whole, the flaky structure of the washcoated catalyst was preserved after coating.