High red photoluminescence emission has been obtained at room temperature in Eu3+-doped yttrium oxide thin films following thermal treatment. Films with different thicknesses were deposited on Si(1 0 0) and Si(1 1 1) substrates via electron beam evaporation in a vacuum environment. The films were subsequently annealed in an oxygen atmosphere for 5 h at 900 C. The structural and optical properties of the films were measured before and after annealing. An improvement in the emission intensity was observed as a result of the thermal treatment under a controlled atmosphere. This observation is related to the reduction of non-radiative processes, as verified by the enhancement of the 5D0→7F2 lifetime values. This improvement in the emission intensity was also analyzed in terms of electric and magnetic dipole transitions (5D0→7F 2 and 5D0→7F1 level transitions, respectively). Both transitions are directly related to the site symmetry and, consequently, to the crystalline structure of the films deposited on the Si(1 0 0)/Si(1 1 1) substrates.