In the present paper, Na3BiO4-Bi2O3 films have been tested for hydrogen ion sensing. Na3BiO4-Bi2O3 mixed oxide nanostructures were deposited on the Indium-Tin-Oxide (ITO) coated glass substrate using a low-cost electrodeposition technique at room temperature. The nanostructures have been characterized using FESEM and XPS to study their morphology and composition, respectively. Vertically aligned nanostructures (thickness similar to 90 nm) with well-defined edges were seen in FESEM studies. XPS analysis indicates the presence of Na3BiO4 and Bi2O3. The crystallinity and the mixed phase of the film were further confirmed by X-ray diffraction study. These nanostructures were explored as a potential candidate for pH sensing using them as a sensing film for Extended-Gate Field-Effect Transistor (EGFET). A sensitivity of 49.63 mV/pH has been observed with good linearity. To the best of our knowledge, for the first time vertically aligned Na3BiO4-Bi2O3 mixed oxide nanostructures are demonstrated as an EGFET-based (Hydrogen ion) pH sensor. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.