Uniform fibers composed of two concentrations of poly(vinyl alcohol) (PVA) separately reinforced with up to 20 wt% cellulose nanocrystals (CNCs) were successfully produced by electrospinning. The CNCs were well dispersed in both 5 wt% PVA (5PVA) and 7 wt% (7PVA) aqueous solution prior to nanofiber manufacture. Composite nanofibers with controllable ultra-thin diameters of around 200 nm were generated reproducibly at all CNC contents investigated, and the nanofiber diameter turned out to be much smaller at higher CNC content. Interestingly, with the same CNC loading, nanofibrous mats produced from 7PVA reinforced with CNC nanoparticles had higher degree of crystallinity than nanocomposite with 5PVA as the matrix due to the more orderly stack of 7PVA nanofibers as well as the stronger interactions between PVA molecular chains and CNC nanoparticles. High mechanical performance nanocomposite fibrous mats were successfully fabricated by electrospinning an all-aqueous system for their potential application in biological field. (C) 2016 Elsevier Ltd. All rights reserved.