A simplified mechanism for the depolymerization of nylon-66 and nylon-6 mixtures via the ammonolysis route is proposed here. The mechanism includes the amide link breakage and amide end dehydration (nitrilation) reactions, plus the ring addition and ring opening reactions for cyclic lactams in nylon-6. On the basis of the proposed mechanism, a kinetic model has been developed for the ammonolysis of nylon mixtures. Model predictions and results from parametric studies are presented and discussed.