A new fluorooxoborate, BaB₈O₁₂F₂, was obtained in this study. It inherits the structural merits of α-BBO (large polarizability of the B₃O₆ groups) and the nearly parallel arrangement of [B₄O₆F]_∞ layers in CBF. First-principles calculations show that BaB₈O₁₂F₂ exhibits a large bandgap (6.85 eV) and possesses a large birefringence of 0.116 at 1064 nm.