Yb2+-doped NaBaPO4 phosphors were synthesized by the conventional high-temperature solid-state reaction. The x-ray powder diffraction, photoluminescence excitation and emission spectra, and the decay curves, were measured. The crystallographic site-occupations of Yb2+ ions in NaBaPO4 host were assigned on the base of the luminescence spectra and the crystal structure. The luminescence natures of NaBaPO4:,Yb2+, e.g., the Stokes shift, the luminescence quenching temperature, and the activation energy of thermal quenching were reported. The thermal stability of luminescence was investigated on the base of the temperature-dependent emission intensities and the decay curves. Some anomalous luminescence properties, e. g., the larger Stokes shift, the short decay lifetimes, the lower quenching temperature and low activation energies for thermal quenching, were discussed. The luminescence was ascribed to impurity trapped exciton emission. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3556095] All rights reserved.