Rare-earth borohydrides have recently attracted a strong interest as potential hydrogen storage materials. While the local structure of the BH₄ ⁻ ion can be probed using vibrational spectroscopy, the local structure of the rare-earth ion can be studied using luminescence spectroscopy. This is reported here for Tb(BH₄)₃ and its solvate with S(CH₃)₂. The spectra clearly show smaller CF splittings for the unsolvated compound. These experimental data are compared with recent DFT+U calculations of the energy levels and CF splittings for Tb(BH₄)₃ and show that these calculations significantly overestimate the experimental results.