Proteins are well-known by their numerous active functional groups along the polypeptide chain. The variety of functional groups of proteins provides a great potential for proteins to interact with airborne pollutants with varying surface properties. However, to our knowledge, a successful demonstration of this potential has not been reported before. In this work, soy protein, a type of abundant plant protein, has been employed for the first time to fabricate multifunctional air-filtration materials. To take advantage of the functional groups of soy protein for air filtration, the soy protein was first well denatured to unfold the polypeptide chains and then fabricated into nanofibers with the help of poly(vinyl alcohol). It was found that the resultant nanofabrics showed high filtration efficiency not only for airborne particulates with a broad range of size but also for various toxic gaseous chemicals (e.g., formaldehyde and carbon monoxide), a capability that has not been realized by conventional air-filtering materials. This study indicates that protein-based nanofabrics are promising nanomaterials for multifunctional air-filtration applications.