One-dimensional composite nanofibers were generated via in-situ polymerization of polyaniline on the surface of tobacco mosaic virus (TMV) and the head-to-tail assembly of TMV. These composite nanofibers have very high aspect ratio and good processibility. Two factors contribute to the formation of such TMV-composite fibers: (1) the accumulation and polymerization of monomers on the surface of TMV; and (2) the possibility of prolongation and stabilization of TMV helices. This strategy has been used in the synthesis of other polymeric bionanofibers with a variety of starting materials. In addition, the morphology of the final composite materials can be modulated by the covalent modification of TMV. When sulfonic acid groups are tailored to the exterior surface of TMV, polymerization of aniline can induce TMV to form branched structures with knot-like connections. On the other hand, modification of TMV with noncharged groups like acetylenes can block the assembly process completely. TEM and AFM are used to analyze the morphology and structure of composite fibers. This novel strategy to assemble TMV into 1D supramolecular assembly could be utilized in the fabrication of advanced materials for potential applications including electronics, optics, sensing, and biomedical engineering.