Hydrothermal synthesis facilitates the hierarchical growth of hexagonal WO3 nanofibers that consist of high interactive space and surface area. Prime processing parameters known as hydrothermal temperature, time and directional growth reagent sodium chloride concentration synchronizes both of the hexagonal crystal structure and nanostructured 10 fibrous morphology of WO3. Hexagonal nanofiber WO3 has specific surface area of 25.2 m(2)/gm and their dip coated WO3/ITO glass substrate exhibits uniform thickness, interconnectivity and high degree of electrochromic properties. The optimized dip coated electrode depicts the current density of 8.9 mA/cm(2), excellent cyclic stability and the coloration efficiency in high acidic electrolyte solution. Crystal structure, morphology formation and their electrochromic responses are illustrated to support the fabrication of electrochromic device. (C) 2014 Elsevier Ltd. All rights reserved.