Thin films of molybdenum oxide were grown by thermal oxidation of DC magnetron sputtered metallic molybdenum films. The deposited molybdenum metal (Mo) films were annealed in air at different temperatures in the range of 473-673 K. The effect of annealing temperature on the structural, morphological, electrical, optical and electrochemical properties was systematically investigated. X-ray photoelectron spectroscopy, X-ray diffraction and Raman studies conformed that the molybdenum films annealed at 573 K leads to the growth of mixed phase of -and -MoO 3 . While those films annealed at 673 K showed single phase of -MoO 3 . The -MoO 3 films were of polycrystalline nature with crystallite size of 22 nm and optical band gap of 3.31 eV. The electrical resistivity of the Mo films is 6 × 10 −5 cm and it was increased to 3.2 × 10 −3 cm when the films annealed at 673 K. From the electrochemical studies, it is observed that, the films annealed at 673 K showed good electrochromic and cyclic voltammetric response.