Sm3+ doped Na3MgZr(PO4)3 phosphor was prepared using high temperature solid state reaction and characterized through X-ray diffractometer (XRD) to identify the crystalline phase. The site occupation of Sm3+ in Na3MgZr(PO4)3 was discussed based on the XRD and crystal structure analysis. The photoluminescence emission spectra showed that Na3MgZr(PO4)3:Sm3+ could absorb near-ultraviolet light around 403 nm and emit red emissions with dominated peaks at 600 and 647 nm, ascribed to the 4G5/2 to 6H7/2 or 6H9/2 transitions of Sm3+ ions, respectively. The optimal doping concentration, the critical distance as well as the interaction mechanism of Sm3+ in Na3MgZr(PO4)3 were discussed. Moreover, the temperature dependent luminescent properties were measured and revealed that Na3MgZr(PO4)3:Sm3+ had excellent thermal stability.