The mechanistic details of the Cu-catalyzed amidation of aryl iodides are presented. The kinetic data suggest that the diamine ligand prevents multiple ligation of the amide. The formation of an amidocuprate species external to the catalytic cycle helped to rationalize the dependence on diamine concentration and the inverse dependence on amide concentration at low diamine concentrations. The intermediacy of a Cu(I) amidate was established through both its chemical and kinetic competency.