A crystallized transparent Li4Ti5O12 thin film is deposited on a fluorine-doped tin oxide (FTO) transparent conducting glass by a pulsed laser deposition method. The transparent Li4Ti5O12 electrode turns dark blue after the injection of Li ions and electrons in an electrochemical cell using a nonaqueous electrolyte. Coloring and bleaching times (700 nm) are 17 and 14 s, respectively, according to in situ UV-visible measurement. The highest contrast between the bleached and colored states is observed at a wavelength of 705 nm, with a variation in the transmittance of 45.8%. The above results confirmed that Li4Ti5O12 is an electrochromic active material with good stability, high switching speed, and color efficiency. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3430658] All rights reserved.