CO₂ methanation is receiving special attention nowadays due to the urgent environmental and energy need to control/recycle CO₂ emissions. Herein the reaction is investigated over mono- and bi-metallic RuNi catalysts supported on mesoporous MCM-41 materials. Monometallic-Ru catalysts were always superior to their monometallic-Ni counterparts, while the bimetallic-RuNi, although outperforming monometallic-Ni, were inferior to monometallic-Ru. The CO₂ methanation efficiency of monometallic-Ni catalysts was found to be highly dependent on the catalyst preparation method: One-pot synthesis provided catalysts almost completely ineffective for methanation, but very effective for the reverse-water–gas-shift (RWGS) reaction producing syngas at low temperatures. In striking contrast, compositionally identical Ni catalysts prepared by impregnation were efficient in CO₂ methanation. An important for practical purposes redispersion of already stabilized large Ni crystallites was achieved by adding small amounts of Ru via the formation of core(Ru)-shell(Ni) nano-configurations. Detailed characterizations, kinetic and in-situ DRIFTS studies allowed the convincing interpretation of the novel findings.