Single crystals of NaBa4Al2B8O18Cl3 have been grown with sizes up to 34 x 34 X 16 mm(3) from the NaF-LiCl flux by the top-seeded solution growth method. The compound crystallizes in the tetragonal system, space group P4(2)nm, with a = 12.0480 (16) angstrom, c = 6.8165 (11) angstrom, alpha = beta = gamma = 90 degrees, and two formula units per cell. The NaBa4Al2B8O18Cl3 compound is built up of infinite anionic groups of [AlB4O12](9-) formed by two BO4 tetrahedra, one AlO4 tetrahedra, and two BO3 triangles. Optical properties including ultraviolet transmission, IR spectrum, and second-harmonic generation of NaBa4Al2B8O18Cl3 crystals were reported. Refractive indices were measured by the minimum deviation technique and fitted to the Sellmeier equations. Thermal properties such as the DSC and thermal expansion were reported. The mechanical properties including the hardness, density, and chemical stability were also reported.