The CO₂ methanation reaction of reduced and unreduced Ni based CeO₂, Al₂O₃, TiO₂ and Y₂O₃ supported catalysts was investigated. The Ni/CeO₂ and Ni/Y₂O₃ catalysts exhibited similar CO₂ conversions at all reaction temperatures. The catalysts were studied by X-ray diffraction (XRD), H₂ chemisorption, H₂ temperature-programmed reduction (TPR), and in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS); the results suggested that the reducibility of both metal and support at low temperature, strong metal support interaction and small Ni particle size are important factors for low-temperature CO₂ methanation. Based on the DRIFT studies, the difference in the CO₂ adsorption properties and reaction pathway depending on the reduced and unreduced Ni based supported catalysts was discussed.