Surface wettability is an important parameter that affects nucleate boiling. Irradiation can alter the surface wettability on metal surfaces without altering the surface macrostructure. However, the wettability characteristics of indium tin oxide (ITO) and TiO2 film-coated sapphire substrates remain unknown. We experimentally investigated the gamma-ray and electron beam irradiation effect on such surfaces. A sapphire plate was exposed to gamma rays and electron beams. Within the irradiation dose, no evident change in the sapphire surface color was found. The surface contact angle decreased after irradiation, and surface wettability was enhanced with more irradiation. After irradiation, the contact angle recovered with time. The related mechanism is possible due to the absorption/desorption of hydroxyl groups. Our results indicate that the irradiation method can be used in ITO film-coated sapphire experiments to study nucleate boiling.