A facile and efficient cyclization of homotryptamines and their derivatives has been established for the construction of 4a‐chlorotetrahydropyrido[2,3‐b]indoles and 3,3‐spirocyclic 3H‐indoles using hypervalentiodine (1‐chloro‐1,2‐benziodoxol‐3‐one) under mild conditions. The broad substrate scope and successful gram‐scale experiment grant this metal‐free transformation great potential for further