A new noncentrosymmetric polyborate, Li4Cs3B7O14, has been synthesized using the conventional solid state reaction method. It crystallizes in the trigonal space group P3(1)21 (No. 152) with unit cell parameters of a = 6.9313(6) angstrom, c = 26.799(3) angstrom, and Z = 3. The new structure contains an infinite three-dimensional matrix that is built from B7O14 building blocks rarely found in anhydrous borate compounds and LiOn (n = 4, 5), CsOn (n = 9, 10) polyhedra. The optical characterization of the compound indicates that the compound is phase matchable, and the UV cutoff edge is below 190 nm. IR spectroscopy, thermal analysis, and second-harmonic generation were also performed on the reported material.