Exploring new photoexcited phosphors has attracted attention for improving the performance of white LEDs. Here, an NaBa4Al2B8O18Cl3:xEu2+ phosphor with high color purity (94.11%) has been synthesized. The NBAC:0.035Eu2+ phosphor exhibits excellent color stability when the temperature increases from 298 K to 473 K. Impressively, the NBAC:0.035Eu2+ blue phosphor still exhibits excellent chemical stability after being immersed in water for 25 days. In addition, Eu2+ ions preferentially occupy the Na/Ba sites of the host structure, which contributes to the superior photoluminescence performance. Furthermore, near-ultraviolet (n-UV) pumped phosphor-converted white light-emitting diodes (pc-WLEDs) have been fabricated using the NBAC:0.035Eu2+ blue phosphor, green commercial phosphor (Sr,Ba)2SiO4:Eu2+ and red commercial phosphor (Ca,Sr)AlSiN3:Eu2+. The resulting device shows uniformly distributed warm white light with a color-rendering index (Ra) of 89.2 and a low correlated color temperature (CCT) of 4153 K. A series of excellent characteristics of NBAC:0.035Eu2+, including high-performance optical characteristics, a simple synthesis process and low economic cost, support its great application potential for use in warm white LED lighting systems.