Color-tunable Ca10Na(PO4)(7): Eu2+, Mn2+ phosphors were firstly synthesized via high-temperature solid-state method. At 350 am NUV excitation, Ca10Na(PO4)(7): Eu2+, Mn2++ emits a broad yellow band and a intense red band, which nearly covers the entire visible region. The mechanism of Eu2+ Mn2+ energy transfer is found to be a quadrupole-quadrupole interaction, and the corresponding critical transfer distance is calculated as 8.24 angstrom. Emission color of Ca10Na(PO4)(7): Eu2+, Mn2+ can be easily modulated from yellow to reddish-orange by adjusting the Mn2+ content. Results indicated that Ca10Na(PO4)(7): Eu2+, Mn2+ might be promising for NUV LED application as an orange-emitting phosphor. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.