Ni-doped SnO2 nanofiber array was prepared from a modified electrospinning technique followed with hot-press and calcination, which impart the nanofiber with high crystallinity as well as good adhesion to the substrate. The nanofiber array consists of well-aligned straight fibers with an average diameter of 200 nm and length of several millimeters. Each fiber consists of rutile-structured polycrystals with an average grain size of 5 nm. Conductometric gas sensors were developed from the nanofiber array using magnetron sputtering. These sensors show excellent performance for NO2 detection at 250 degrees C, including high response (90.3 under 20 ppm), fast response and recovery (40 s/18 s), and above all, excellent selectivity. Beneficial for electron transport, the nanofiber array offers better device performance over random nanofibers on sensing response and time for recovery. In addition, the NO2 sensing mechanism was probed with detailed DRIFT and XPS analysis. (C) 2017 Elsevier B.V. All rights reserved.