A series of Ce1-xMnxO2-δ (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) nanocatalysts were prepared by solution combustion synthesis. XRD results confirmed the absence of bulk manganese oxide in Ce1-xMnxO2-δ indicating the substitution of Mn ion in ceria matrix. The percentage C and N doping in Ce1-xMnxO2-δ was quantified with a CHN analyzer, whereas, the mesoporous nature of the catalysts was confirmed by N2 physisorption analysis. Raman, H2-TPR results confirmed the increasing oxygen vacancies on Mn substitution, whereas, UV-VIS DRS and XPS confirmed the multiple oxidation states of Mn ion. SEM and TEM analysis highlighted the near spherical morphology and nanoparticle size, respectively. The rate of CO oxidation was found to be the highest for Ce1-xMnxO2-δ (x=0.2), which was assigned due to the combined effect of highest amount of Mn+2 and/or due to the highest oxygen vacancies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim