The partially polarized luminescence of erbium- and thulium-doped glasses exited by the linearly polarized laser radiation was observed. The dependence of the polarization degree on the RE ions concentration and on the glass matrix composition were investigated. For erbium- and thulium-doped glasses, the maximum polarization degree was shown to reach ∼0.1% and ∼1%, respectively. The polarized luminescence properties of RE-doped glasses were explained based on the model of an optical oscillator.