A series of single-phased emission-tunable Na(0.34)Ca(0.66)Al(1.66)Si(2.34)O(8):Eu(2+),Mn(2+) phosphors were successfully synthesized by a wet-chemical synthesis method. Photoluminescence excitation (PLE) spectra indicate that the phosphor can be efficiently excited by UV radiation from 250 to 420 nm. Also, NCASO:Eu(2+),Mn(2+) phosphor exhibit a broad blue emission band at 440 nm and an orange emission band at 570 nm, which originate from Eu(2+) and Mn(2+) ions, respectively. Therefore, overall emission color can be tuned from blue to white by increasing the concentration of Mn(2+) ions in the host lattice utilizing energy transfer from Eu(2+) to Mn(2+) ions. This energy transfer phenomenon was demonstrated to be a resonant type through dipole-dipole interaction determined with the help of PL spectra, decay time measurement, and energy transfer efficiency of the phosphor. These results indicate that NCASO:Eu(2+),Mn(2+) can be a promising single-phased white-emitting phosphor for white-light UV LEDs.