Polycrystalline ZnSe thin films were grown by ion‐beam deposition on glass substrates. The crystallinity of ZnSe films grown by ion‐beam deposition is affected by ionization. In particular, at a substrate temperature of 200 °C, there is an abrupt increase in the number of (311) oriented grains. Without ionization, the (111) oriented grains predominate. Transmittance of ZnSe films is improved by ion‐beam deposition at substrate temperatures below 200 °C, in the wavelength range of 460–550 nm near the interband absorption edge. Ion‐beam deposition has a heating effect on the film surface during deposition by ion bombardment, which controls the crystallinity and the optical properties of ZnSe films at low substrate temperature on noncrystalline substrates.