Undoped single crystals of Lu3Al5O12 annealed in the reduced atmosphere or additively colored in Al vapors were studied at 4.2–400 K by the time‐resolved spectroscopy methods. The 3.15 eV emission, excited in the 3.4, 5.3, and 6.1 eV absorption bands and having a decay time of 3.14 ns at 10 K, was ascribed to the F+‐type centers. It was suggested that these centers consist of an oxygen vacancy with one trapped electron which is perturbed by the neighboring antisite defect (Lu Al3+) or an impurity ion at the Al3+ site. The small Stokes shift and half‐width of the emission band indicate that the F+‐type centers are characterized by a weak electron–phonon interaction.