Electrospun polymer nanofibers have been actively studied in both academic and applied research. Ion conductive nanofibers in particular have attracted considerable attention owing to their unique characteristics and potential applications in electrochemical devices. This Focus Review summarizes our recent work on the development of ion conductive nanofibers and their application to polymer electrolyte fuel cell membranes. Recent research trends on ion conductive nanofibers are described along with a brief overview of the fabrication, properties and applications of polymer nanofibers. In our recent studies, we succeeded in evaluating the intrinsic proton and anion conductivity of electrospun nanofibers and revealed their distinguished ion conductive properties, which were quite different from those of the corresponding polymer membranes. These ion conductive nanofibers have potential utility as polymer electrolyte membranes to improve fuel cell performance by utilizing efficient ion conduction both inside and at the surfaces of nanofibers.