Magnetic-luminescent bifunctional flexible Janus nanofibers have been successfully fabricated via electrospinning technology using a homemade parallel spinneret. NaYF4:Tb3+ and Fe3O4 nanoparticles (NPs) were respectively incorporated into polyvinyl pyrrolidone (PVP) and electrospun into Janus nanofibers with NaYN4:Tb3+/PVP as one strand nanofiber and Fe3O4/PVP as another strand nanofiber. The morphologies, structures, magnetic and luminescent properties of the as-prepared samples were investigated in detail by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), vibrating sample magnetometry (VSM) and fluorescence spectroscopy. The results show Janus nanofibers simultaneously possess superior magnetic and luminescent properties due to their special structure, and the luminescent characteristics and saturation magnetizations of the Janus nanofibers can be tuned by adding various amounts of NaYE4:Tb3+ NPs and Fe3O4 NPs. Compared with Fe3O4/NaYN:Tb3+/PVP composite nanofibers, the magnetic-luminescent bifunctional Janus nanofibers provide better performances due to isolating NaYF4:Tb3+ NPs from Fe3O4 NPs. The novel magnetic-luminescent bifunctional Janus nanofibers have potential applications in the fields of new nano-bio-label materials, drug target delivery materials and future nanodevices owing to their excellent magnetic and luminescent performance. More importantly, the design conception and construction technology are of universal significance to fabricate other bifunctional Janus nanofibers. (C) 2014 Elsevier B.V. All rights reserved.