Ni/La₂O₃–αAl₂O₃ catalysts were characterized and tested in the methane tri-reforming reaction. The catalysts were prepared by the combustion method, and characterized by nitrogen physisorption, SEM, XRD, and Rietveld refinement, H₂-TPR, and CO₂-TPD. The metallic dispersion of Ni in the catalysts increased with the addition and increase of La₂O₃ amount. The reaction tests showed that the addition of La₂O₃, and the consequent increase in the metallic dispersion of Ni, influenced the catalytic results, favoring the selectivity towards H₂ production, leading to higher resistance to carbon deposition on the catalyst surface. However, there was a decrease in the selectivity towards H₂ and a higher rate of carbon deposition for catalysts with a higher additive content, having its maximum even with the increase in Ni dispersion, with the catalyst N10LαA. This result suggests that there was a limit for the La₂O₃ content, above which there would no longer be observed beneficial effects for the reforming process. The N2.5LαA catalyst showed the highest selectivity towards H₂ and the lowest carbon deposition rate among the catalysts.