Nanocrystalline bismuth telluride (Bi2Te3) thin films with good thermoelectric performance were prepared using mixtures of hydrogen and argon gas by radio-frequency magnetron sputtering. The effects of hydrogen addition on the surface morphology, crystal structure, elemental composition, and thermoelectric properties of the Bi2Te3 thin films were investigated. The mixing ratio, H-2/(H-2 + Ar), was varied from 0 to 15%. The thin films were deposited on glass substrates heated at 200 degrees C. It was observed that the surface morphologies of the thin films were greatly affected by the mixing ratio. The deposition rate and composition ratio Te/(Bi +Te) decreased with increasing mixing ratio, indicating that tellurium atoms evaporated from the film surface by a chemical reaction between hydrogen and tellurium. The oxygen concentration inside the films decreased as the mixing ratio increased, resulting in an increased power factor. A maximum power factor of 9.0 mu W/(cm-K-2) was observed at a mixing ratio of 10%, as this thin film showed a relatively high electrical conductivity and high Seebeck coefficient. However, at a higher mixing ratio of 15%, the power factor of the thin film drastically decreased, possibly due to the appearance of the hexagonal BiTe phase, which exhibits metallic characteristics. Therefore, we conclude that the addition of a moderate amount of hydrogen (10%) during sputtering can improve the thermoelectric performance of Bi2Te3 thin films.