Abstract The dynamics of nitrogen adsorption on the W(100)-c(2 × 2)Cu surface have been studied with a supersonic molecular beam. Both associative and dissociative adsorption is observed. The molecular and atomic species desorb at 200 K and 1100 K, respectively, reflecting a decrease in the thermal stability of the atomic state, and an increase for the molecular state, relative to the W(100) surface. Dissociation on the alloy surface takes place entirely via a direct channel which presents an activation barrier of 0.6 ± 0.1 eV. This is significantly increased from that observed on W(100). Concomitant with the increase in the direct channel barrier on the alloy, we observe the complete blocking of the large indirect dissociation channel observed on W(100). Adsorption into the molecular state is non-activated, and shows very similar dynamics to those on W(100).