The effects of an iridium (Ir) electrode on the properties of Ba0.5Sr0.5TiO3 (BST) films were studied, in comparison with a conventional platinum (Pt) electrode. It was found that the dielectric constant of BST films is strongly dependent on the electrode material. The BST films deposited on an Ir bottom electrode were preferentially oriented and showed higher dielectric constants than those on Pt. Higher dielectric constants of the BST films could also be obtained by using Ir instead of Pt as a top electrode material, which was explained as being due to the compressive stress in the BST film induced by the Ir top electrode.