Bismuth telluride (Bi2Te3) thermoelectric thin films were deposited on polyimide substrate by radio-frequency (RF) magnetron sputtering technique. The structural and thermoelectric properties of the films were investigated under the annealing temperatures. As-deposited films were annealed in the vacuum chamber with the N2 flow gases at three different temperatures of 300, 350, and 400°C for 1 hour. The crystal structures and microscopy of the films were characterized by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope(FE-SEM), respectively. Seebeck coefficient and electrical resistivity of the films were simultaneously measured at room temperature and up to 150 C by dc four-terminal method (ZEM- 3). It was found that the Seebeck coefficient and electrical resistivity decreased with increasing temperature. The film annealed at 400 C has a maximum PF value of 1.41 x 10-3 W/m.K2 at the applied temperature of 150 C.