Abstract Lithium haloborate glasses have been prepared according to the formula (70− y)B 2O 3–30BaF2– yLiX where y=0, 5, 10, 15 and 20 mol% and X=F, Cl and Br. The UV absorption spectra have been recorded at room temperature. The optical energy band gap E opt and Urbach energy E tail was determined. Increasing concentration of LiX in the glass shifts the UV cutoff to lower energy and decreases both E opt and E tail . The shift in UV cutoff and the decrease of E opt and E tail are maximum in the range 0–5 mol% LiX. The decrease of E opt increases going from F, Cl to Br, whereas the decrease of E tail increases going from Br, Cl to F. At higher LiX concentrations Urbach energy E tail increases again. The behavior of E opt has been correlated with the B–O bond length of the studied glasses. The decrease of E opt and E tail is due to the increase of nonbridging oxygen (NBO) concentration with increase of LiX content. The increase of E tail at higher concentrations is attributed to the halide ion accumulation in the interstitial positions and to the formation of orthoborate groups. Refractive index, which is measured and calculated, molar refraction and polarizability are all correlated with the composition of the glasses.