Recent developments in nanocomposites that are reinforced with polymeric fibers have heightened the need for a material in fast-moving parts of machines. The research to date has focused on tensile properties of nanocomposites reinforced with polymeric nanofibers, which were produced by the conventional methods. In this work, nanocomposites were fabricated by a novel approach that comprises epoxy resin, epoxy hardener, and PAN nanofibers in which the nanofibrous layer was placed in resin as spun during the electrospinning. Then, a nanocomposite with the same materials was made using the conventional method of layering. There were enhancements in elongation at break, fracture toughness, and stress at break of nanocomposites fabricated by in situ method in comparison with the nanocomposites fabricated using the conventional method of layering.