Single crystal of a new ternary boride NaAlB 14 was grown from a high temperature Al solution using Na 2 B 4 O 7 and crystalline boron powders as raw materials under an Ar atmosphere. The crystals obtained showed a plate-like or a trapezoidal shape with well-developed {010} faces, and were reddish black with a metallic luster. The largest crystal prepared in the present work attained maximum dimensions of approximately 7.3mm×3.2mm×2.8mm. The crystals were examined by powder X-ray diffraction and chemical analyses, and the crystal structure of NaAlB 14 was refined using data of single crystal X-ray diffractometry. The structure refinement converged at an R1 (F 2 ) value of 0.025 with 29 parameters for 381 independent reflections [F 0 >4σ(F 0 )] and 0.027 for all 426 independent reflections. The crystal structure is orthorhombic with the space group Imma (number 74), and lattice constants are a=1.0465(1), b=0.5844(1), and c=0.8231(1)nm; V=0.5034(1)nm 3 ; Z=4.