A radical-mediated, one-pot, multicomponent cascade reaction was developed for the synthesis of azide-biindole derivatives. Mechanistic studies demonstrated that the nitrogen-centred free radical was formed by the reaction of heterocyclic N-H with CuII and PIFA and initiated the cascade reaction with indole to obtain the biindole intermediate. The biindole intermediate then reacted with sodium azide in the presence of CuII catalyst and PIFA to form the final products. This methodology may be useful for constructing other azido heterocycles.