A series of new luminescent emission-tunable phosphors Ca 9Y(PO4)7:zCe3+,xMn2+ have been synthesized by a high-temperature solid-state reaction. We report a broad deep red-emitting composition-optimized phosphor (Ca0.9) 9Y0.85(PO4)7:0.15Ce 3+,0.1Mn2+, which has been found to be feasible for the application in fluorescent lamps. The Commission Internationale de I'Eclairage (CIE) chromaticity coordinates measured for the phosphor were (0.68, 0.29), and those for fluorescent lamps with and without a 600 nm filter were found to be (0.67, 0.29) and (0.54, 0.32), respectively. The Ca9Y(PO 4)7:Ce3+,Mn2+ phosphor showed two emission bands under 254 nm excitation: the one observed at 366 nm was attributed to Ce3+ ion emission, and the other found at 650 nm was assigned to the emission from Mn2+ ions. We have shown that the mechanism of energy transfer from Ce3+ to Mn2+ was of the resonance type and it occurred via an electric dipole-quadrupole interaction. Furthermore, we have calculated the critical distance for Ce3+ → Mn2+ energy transfer to be 13.45 Å by concentration quenching methods.