Preliminary activity tests showed a synergistic effect on the yield of N2O decomposition by the addition of small quantities of rhodium in a Ag/Al2O3 catalyst. An analytical comparative kinetic study over Rh/Al2O3, Ag/Al2O3, and Rh-Ag/Al2O3 was performed in order to explain this effect. In the absence of oxygen, the reaction kinetics over the silver catalyst seemed to follow a L-H mechanism with N2O inhibition; in the case of rhodium, the power law equation was applied. While in the case of the mixed catalyst, a L-H mechanism was followed and the inhibition effect was not observed for the studied condition. From the results of the kinetic study, it seemed that the synergistic effect was connected with an increase of the catalytic activity over both silver and rhodium catalysts, since more active sites were offered and N2O inhibition became less intensive. The presence of oxygen was found to inhibit the reaction over the silver and the mixed catalysts, but the inhibition effect was less intensive in the case of the mixed catalyst.