We report a facile approach to immobilizing gold nanoparticles (AuNPs) into electrospun polyethyleneimine (PEI)/polyvinyl alcohol (PVA) nanofibers for catalytic applications. In this study, electrospun PEI/PVA nanofibers with a mean diameter of 490 nm were first crosslinked with glutaraldehyde vapor to render them water stable. Then, the water-insoluble nanofibrous mats were used as nanoreactors to complex AuCl4− anions via binding with the free aminegroups of PEI for subsequent formation and immobilization of AuNPs. The formed AuNPs with a diameter of 11.8 nm within the nanofibers do not significantly change the morphology of the nanofibers; while importantly the mechanical property of the fibers was greatly improved compared to the crosslinked fibers without AuNPs. Scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive spectroscopy, and thermogravimetric analysis were used to characterize these hybrid nanofibers. Furthermore, we show that the AuNP-containing nanofibers display an excellent catalytic activity and reusability for the transformation of 4-nitrophenol to 4-aminophenol. The present approach to fabricating AuNP-containing nanofibers may be extended for producing other nanoparticle-containing composite nanofibrous materials for various applications in catalysis, sensing, and biomedical sciences.