Thin films of Bi2(Te0.4Se0.6)3 alloy have been flash evaporated on to clean glass plates held at room temperature in a vacuum of 2×10-5 torr. The films are found to be polycrystalline with fine grains. Grain growth and grain re-orientation take place in the film during the annealing process. Grain size of the films is found to increase with the increase of thickness of the films. The annealed films have been used for the size effect studies of electrical resistivity and thermoelectric power. Conduction activation energy is found to be thickness dependent. This is ascribed to the polycrystalline nature of the films. The size effect analysis leads to the evaluation of important physical parameters like mean free path, Fermi energy and exponent of the energy dependent expression for the mean free path. Carrier concentration is calculated using the Fermi energy obtained from the size effect analysis.