We compare two different transparent conducting oxides (TCO), namely indium tin oxide (ITO) and indium tungsten oxide (IWO), as substrates for the preparation of electrochromically active tungsten oxide (WO3) thin films by ultrasonic spray pyrolysis. The ITO- and IWO-coated glass substrates were prepared by magnetron sputtering at low temperatures, an interesting alternative to chemical vapor deposition at high temperatures. We report the electrochemical and electrochromic characteristics of WO3 deposited on the ITO-and IWO-coated glass substrates. Due to the application of WO3 as electrochromic material, particular attention was paid to the electron and ion transport, the cycling response, and the coloration/bleaching optical modulation and kinetics of the WO3 layer. The results are discussed in relation with the morphology, crystallinity and conductivity of the ITO/IWO layer. (C) 2016 The Electrochemical Society. All rights reserved.