A gold(I)/Brønsted acid-catalyzed cyclization of 2-azidobenzaldehydes with 3-aza-1,6enynes has been developed for the synthesis of tetrahydrobenzo[b] [1,8]naphthyridine derivatives. This protocol enabled the modular synthesis of tetracyclic heterocycles in one operation with water and nitrogen gas as the byproducts.