In this study, Ni catalysts supported on Pr-doped CeO₂ are studied for the CO₂ methanation reaction and the effect of Pr doping on the physicochemical properties and the catalytic performance is thoroughly evaluated. It is shown, that Pr³⁺ ions can substitute Ce⁴⁺ ones in the support lattice, thereby introducing a high population of oxygen vacancies, which act as active sites for CO₂ chemisorption. Pr doping can also act to reduce the crystallite size of metallic Ni, thus promoting the active metal dispersion. Catalytic performance evaluation evidences the promoting effect of low Pr loadings (5 at% and 10 at%) towards a higher catalytic activity and lower CO₂ activation energy. On the other hand, higher Pr contents negate the positive effects on the catalytic activity by decreasing the oxygen vacancy population, thereby creating a volcano-type trend towards an optimum amount of aliovalent substitution.