We present a convenient method to immobilize Au/Ag nanoparticles (NPs) within electrospun polyvinyl alcohol (PVA)/polyethylenimine (PEI) nanofibers by in-situ reduction for catalytic applications. Water-stable electrospun PVA/PEI nanofibers were initially fabricated by crosslinking with glutaraldehyde (GA) vapor. Then, the nanofibers were used as a nanoreactor to bind Au salt via electrostatic interaction with the free PEI amines, followed by NaBH4 reduction to form Au NPs. The formed Au NP-containing nanofibers were then used to bind Ag+ ions via chelation with the free PEI amines, followed by reduction with ascorbic acid to form the Au/Ag NP-loaded PVA/PEI nanofibers. The small size (4.9 +/- 1.8 nm) and narrow size distribution of the immobilized Au/Ag NPs reveal that the nanofibrous structure is able to efficiently prevent the aggregation of the NPs. We then evaluated the catalytic activity and reusability of Au/Ag NP-immobilized PVA/PEI nanofiers by catalytic transformation of 4-nitrophenol to 4-aminophenol in aqueous solution. The material exhibited excellent catalytic.