We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from nearinfrared to vacuum-ultraviolet and for temperatures 10 K–300K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.