In this work, we have prepared polyacrylonitrile (PAN) polymer nanofibers by electrospinning method. The surface of the electrospun PAN nanofibers membrane has been functionalized with ZnO-Ag heterostructure nanoparticles by using three different chemical pathways such as reflux, blending, hydrothermal methods and accordingly the prepared composite nanofibers membranes were named as PAN/ZnO-Ag (R), PAN/ZnO-Ag (B) and PAN/ZnO-Ag (H) respectively. The obtained heterostructure nanoparticles functionalized PAN nanofibers membranes were characterized using ATR-FTIR, XRD, FESEM and TEM analytical techniques. From the FESEM and TEM images it was clearly observed that 20-30 nm size spherical nanoparticles have been decorated uniformly on the surface of PAN nanofibers. XRD study confirmed the formation of ZnO-Ag mixed/hybrid nanoparticles on PAN nanofibers surface. The ZnO-Ag heterostructure nanoparticles functionalized PAN nanofibers membranes were used for antibacterial application. It was observed from inhibition zone study that the ZnO-Ag heterostructure nanoparticles functionalized PAN nanofibers membrane shows excellent antibacterial properties towards both gram-negative Escherichia coli and gram-positive Micrococcus luteus bacteria than their single component counterparts. Thus this study demonstrated the simple and cost-effective approach to develop antibacterial functional membrane that has many potential applications in water and air filtration, protective mask, textile and packaging industries.