<jats:sec><jats:label /><jats:p>High electron mobility of transparent conductive oxide (TCO) facilitates high conductivity at a moderate carrier density, resulting in an extension of the degree of transparency from visible to near‐infrared due to less free carrier absorption. These broadband TCO electrodes provide opportunities to improve the performance of optoelectronic devices. Herein, the thermal and damp heat stability characteristics of TCO films are described. It is found that the difference in the crystal growth method has a significant influence on the initial electrical properties and stability characteristics. Polycrystalline In<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>:Me (Me: W, Ce) films deposited at 200 °C exhibit a relatively high mobility of 70–80 cm<jats:sup>2</jats:sup> V<jats:sup>−1</jats:sup> s<jats:sup>−1</jats:sup>, are stable after a damp heat test, and improve the mobility of 110–140 cm<jats:sup>2</jats:sup> V<jats:sup>−1</jats:sup> s<jats:sup>−1</jats:sup> after postannealing at temperatures greater than the deposition temperature. Conversely, solid‐phase crystallized In<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>:Me,H films prepared by postannealing amorphous films exhibit an extremely high mobility of 100–160 cm<jats:sup>2</jats:sup> V<jats:sup>−1</jats:sup> s<jats:sup>−1</jats:sup>; however, they exhibit reduced stability characteristics after the damp heat test and high‐temperature annealing process compared to the polycrystalline films. The deterioration of the electrical properties increases as the hydrogen content in the films increases. The results suggest that polycrystalline and solid‐phase crystallized films should be used properly, according to the device manufacturing processes.</jats:p></jats:sec>