A series of mixed 3,3'-bisindoles were efficiently synthesized via a Rh2(OAc)4-catalyzed three-component reaction of 3-diazooxindoles with indoles and ethyl glyoxylate in high yields with excellent diastereoselectivities. The product easily underwent further synthetic transformations and could be potentially applied to the total synthesis of (±)-gliocladin C and related natural alkaloids.