alpha-NaSrBO3 is an excellent phosphor host for phosphor-converted white light-emitting diode (w-LED) application with very interesting properties. However, it undergoes a phase transformation to beta-NaSrBO3 at the LED working temperature. In this study, the high-temperature phase beta-NaSrBO3 was stabilized to room temperature by introducing Na+ and Ce3+ via a high-temperature solid-state reaction method. The crystal structure of beta-NaSrBO3 was determined from the powder X-ray diffraction data. It crystallizes in space group P2(1)/c with the following lattice parameters: a = 6.06214(8) angstrom, b = 5.41005(7) angstrom, c = 9.1468(1) angstrom, beta = 102.116(1)degrees, and V = 293.301(7) angstrom(3). Na and Sr sites are found to be mixed occupied by each other, and the isolated [BO3](3-) anionic groups are distributed in parallel. Ce3+-activated beta-NaSrBO3:Ce3+ blue-emitting phosphors were synthesized. The temperature-dependent photoluminescence spectra indicate that the thermal stability of beta-NaSrBO3:Ce3+ is better than that of alpha-NaSrBO3:Ce3+ at the same temperature. A near-ultraviolet pumped warm w-LED with a beta-NaSrBO3:0.05Ce(3+) phosphor as the blue component was fabricated. The w-LED lamp after illumination at 250 mA gives chromaticity coordinates, a color rendering index, and a correlated color temperature of (0.3821, 0.3430), 92.8, and 3654 K, respectively.