Nanostructured polyaniline (PANI) films with well-defined structures have received great research attention due to their various applications in energy storage and conversion, sensors and catalysis. Herein, an air–water interface polymerization method has been developed to fabricate PANI inverse opal/nanofiber network (IO/NFN) films, with the NFN rooted in the bottom of the IO. Colloidal crystals (CCs) are transferred to the surface of an aqueous aniline solution, where aniline could polymerize on the surface of the CC after addition of an oxidant. With a molar ratio of oxidant to aniline of 3 or larger, PANI nanofibers form at the bottom of the PANI coated CC. After removal of the spheres, a PANI IO/NFN film could be obtained. The top layer of IO is composed of a nanobowl array with pores connected to the underlayers, without being covered by overlayers. Such IO/NFN composite structures represent a new family of Janus materials, providing a platform for various potential applications.