Electrical and optical properties of MoO 3 -TeO 2 amorphous films prepared by vacuum deposition method were investigated. X-ray diffraction patterns show an amorphous structure. The dc conductivity of the films was measured in the temperature range 323-523 K and follows a non-adiabatic small polaron hopping conduction mechanism between Mo 4þ and Mo 5þ , confirmed by X-ray photoelectron spectroscopy measurements. Conductivity of the films increases with increase of MoO 3 content. The Seebeck coefficient indicates the films to be n-type semiconductor. Optical absorption edge analysis gave a band gap energy of 2.7-2.9 eV depending on composition. The Urbach tail analysis gave the width of localized states between 0.23 and 0.25 eV.