Cobalt oxide thin films were prepared by spray pyrolysis technique onto the fluorine doped tin oxide (FTO) coated glass substrates from cobalt chloride solution. They were characterized by cyclic-voltammetry, chronoamperometry and spectrophotometry techniques. The films exhibited anodic electrochromism, changing colour from grey to pale yellow. Colouration efficiency at 633 nm was calculated to be 12 cm(2) C-1.