The catalytic methanation of CO2 with ammonia over Ni, Pt, and Ru catalysts impregnated on gamma-alumina was carried out in a fixed-bed reactor under atmospheric pressure at 573-873 K. The methanation of CO2 with NH3 is considered to occur in two stages-NH3 decomposition into H-2/N-2 followed by CO2 methanation with H-2. 1 wt% Pt/gamma-Al2O3 exhibited low activity for NH3 decomposition and CO2 methanation with H-2. Both 5 wt% Ni/gamma-Al2O3 and 1 wt% Ru/gamma-Al2O3 showed high activity for NH3 decomposition and CO2 methanation with H-2, but Ru/gamma-Al2O3 was much more active. For CO2 methanation with ammonia, only Ru/gamma-Al2O3 was significantly active. The yield of CH4 increased with increased Ru loading and reaction temperature, but was limited by thermodynamic equilibrium at higher temperatures. Ammonia decomposition is more facile than CO2 methanation on the Ru/gamma-Al2O3 catalyst and CO2 methanation is the rate limiting step.