Yttrium oxide (Y2O3) thin films were deposited on indium‐tin‐oxide(ITO)‐coated glass substrates by the radio‐frequency‐sputtering method using an Y2O3‐sintered target. The relative dielectric constant &egr;rand the dielectric strengthEBDof the Y2O3films were studied. It was found that &egr;rand EBDhave a maximum value and a minimum value, respectively, at 1.3 Pa when the pressure of the sputtering gas, Ar+10% O2, is varied from 0.67 to 9.3 Pa. The x‐ray diffraction study showed that the Y2O3films deposited at 1.3 Pa are predominantly oriented along the ⟨332⟩ direction and their grain size is the smallest. Ion mass analysis showed impurity diffusion from ITO in the films deposited at 1.3 Pa. Furthermore, the dielectric properties of the Y2O3films deposited at 1.3 Pa are related to the structural properties, such as the ⟨332⟩ orientation, grain size, and impurity diffusion.