Tungsten tri oxide hierarchical nanostructures (h-WO3) and bismuth oxide (Bi2O3)/h-WO3 nanocomposite successfully prepared via a simple one-pot hydrothermal method. Structural properties of the materials reconnoitered by numerous characterization techniques such as FESEM, EDX, XRD, FT-IR and Raman. FESEM analysis designated that the h-WO3 made of smaller layered nanorods with four axis, while the EDX analysis confirmed the elemental composition of pristine h-WO3 and Bi2O3/h-WO3 nanocomposite respectively. The XRD patterns revealed the formation of monoclinic crystal unit of WO3 product. The as-prepared h-WO3 nanostructures and Bi2O3/h-WO3 nanocomposite displayed strong near-infrared absorption and the Raman spectrum, also indicated characteristic peaks for Bi-O and WO3 vibrations. Based on the structural characterizations, the plausible growth mechanism for the formation of h-WO3 nanostructures proposed. The optical properties of h-WO3 and their nanocomposite studied through UV-Vis spectrometer and decrease in bandgap observed from 2.81 eV to 2.64 eV for the later. The photoelectrochemical (PEC) study indicated that h-WO3 is active under visible-light region and the Bi2O3 incorporation further ameliorated its water splitting properties. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.