Studies on the crystal structure and luminescence properties have been performed for the NaPr_1−xCe_xP₄O₁₂ polyphosphate series. Excitation and emission spectra of Pr³⁺ and Ce³⁺ luminescence from NaPrP₄O₁₂:Ce³⁺ clearly reveal an efficient Pr³⁺  → Ce³⁺ energy transfer via migration over the Pr³⁺-sub-lattice and a nonradiative resonant transfer to the Ce³⁺ ions. Analysis on scintillation characteristics of the NaPr_1−xCe_xP₄O₁₂ series shows a maximum light yield of 11 000 ± 1000 ph MeV⁻¹ for NaPr_0.99Ce_0.01P₄O₁₂, proving the studied polyphosphates to be promising for application in the detection of x-ray and gamma quanta.