Eu3+, Bi3+ codoped Lu2O3 powders (Eu = 2.5 at.%, Bi = 0–3.0 at.%) were prepared using the sol–gel method. Fourier transform infrared spectroscopy, x-ray diffraction, and excitation and emission spectra were carried out to characterize the synthesis, structure, and luminescent properties. The excitation spectra show a strong peak at 350–390 nm, corresponding to the Bi3+1S0 → 3P1 transition, and the emission spectra present the emission from 5D0 → 7FJ (J = 0, 1, 2, 3, 4) level of Eu3+. The intensity of the reddish emission at 612 nm was monitored as a function of the Bi3+ content and showed a light yield increment of ≈400% compared to a monodoped sample at 1.0% at. Bi3+, produced by an energy transfer process from Bi3+ to Eu3+. This was a consequence of the overlapping of the Bi3+3P1 → 1S0 emission with the f–f Eu3+ transitions.