Polyaniline nanofibers and their composite with graphite have been synthesized by a simple chemical polymerization method. Polyaniline nanofiber graphite composites with a thickness of 1 mm exhibit excellent electromagnetic interference (EMI) shielding of above 80 dB in the frequency range of 8.2–18 GHz. EMI shielding fabrics of 0.1 mm thickness based on polyaniline nanofibers and their composite have been developed by an in situ polymerization route. These fabrics combine the properties of polyaniline nanofibers as well as their composite and fabrics (cotton and nylon). The developed functional fabrics with 0.1 mm thickness exhibit EMI shielding effectiveness in the range of 11–15 dB in the 8.2–18 GHz frequency range. Optical and scanning electron microscopy studies indicate the uniform coating of the polyaniline nanofibers over the individual fibers and interweave regions. Thin and flexible shielding materials suitable for a broad range of millimeter-wave shielding applications have been developed using this simple and potentially profitable method. Schematic representation depicts the synthesis, microstructure and EMI shielding properties of functional cotton and nylon fabrics based on polyaniline nanofibers.