This investigation focuses on the manipulation of the physicochemical properties and oxygen defect concentration of europium doped CeO2 by the introduction of a second dopant (co-dopant, M). Accordingly, in this study a series of Ce0.8Eu0.1M0.1O2-δ (M = Zr, Hf, La, and Sm) nano-oxides were prepared and tested for diesel soot oxidation catalysis. The systematic characterization studies indicated successful incorporation of both dopants in the cubic fluorite crystal structure of CeO2. A remarkable enhancement in the reduction properties and oxygen defect concentration was observed for the co-doped samples from structural and chemical analyses. The aliovalent co-doped materials exhibited better performance than the isovalent co-doped materials. The catalytic activity order of the prepared materials towards model soot oxidation was Ce0.8Eu0.1La0.1O2-δ > Ce0.8Eu0.1Sm0.1O2-δ > Ce0.8Eu0.1Hf0.1O2-δ > Ce0.8Eu0.1Zr0.1O2-δ > Ce0.9Eu0.1O2-δ > CeO2. The most favorable modification of the physicochemical properties of europium doped ceria was ascertained in the presence of La as a co-dopant compared to other combinations investigated. The correlation of the physicochemical properties with the catalytic activity has also been clearly demonstrated in the manuscript. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.