Blue-emitting phosphors ABaPO(4):Eu (A = Na, K) are synthesized by the combustion-assisted synthesis method. The formation of single ABaPO(4) (A = Na, K) phases has been confirmed by X-ray powder diffraction (XRD). X-ray photoelectron spectroscopy (XPS) is used to investigate europium valence in the ABaPO(4):Eu (A = Na, K) samples. Evidence is found that the ABaPO(4):Eu (A = Na, K) samples prepared in this paper exhibit a mixed-valence europium state (Eu3+ and Eu2+). Photoluminescence (PL) results show that the NaBaPO4:Eu and KaBaPO(4):Eu phosphors emit a strong blue light under UV excitation.