A self-activated crystal Na 3 Nd 9 O 3 (BO 3 ) 8 has been grown by using Na 2 CO 3 –B 2 O 3 –NaF as flux. Its structure was determined by single crystal X-ray diffraction. Na 3 Nd 9 O 3 (BO 3 ) 8 crystallizes in the hexagonal crystal system, space group P6¯ 2m with unit-cell parameters a = 8.7611 Å, c = 8.4579 Å, Z = 1, and V = 562.23 Å 3 , which is isostructural with Na 3 La 9 O 3 (BO 3 ) 8 . Na 3 Nd 9 O 3 (BO 3 ) 8 has a high Nd 3+ concentration (1.60 × 10 22 ions/cm 3 ), almost three times that of the self-activated crystal NdAl 3 (BO 3 ) 4 (NAB). The absorption and emission spectra as well as decay time for 4 F 3/2 to 4 I 11/2 transition in Na 3 Nd 9 O 3 (BO 3 ) 8 were measured at room temperature. The obtained results show that Na 3 Nd 9 O 3 (BO 3 ) 8 may be a potential high-neodymium-content laser crystal for microchip laser application.