This paper deals with the aging effect on the kinetics of the NO decomposition on a commercial Pd/Al2O3 catalyst. Temporal analysis of products experiments are discussed in the light of a selected mechanism involving the recombination of two NOads species to form N2O, which is an intermediate in N-2 formation. Experiments over the fresh catalyst indicate a strong metal/support interface, with a spill-over effect, which is difficult to model. Thermal aging had a detrimental effect over this interface, the kinetic features depending mainly on the metallic Pd sites. The different heats of adsorption and activation energies are proven consistent with other theoretical studies. The mechanism led to a high surface coverage for O ad-atoms.