A yellow-emitting phosphor, CaO:Ce3 +,Na+ is synthesized by solid-state reaction. The photoluminescence spectra, fluorescence decay curves and the temperature-dependent luminescence are investigated. The results show that CaO:Ce3 +,Na+ can be excited by blue light, which matched well with the emission wavelengths of blue InGaN LED chips. When excited at 474 nm, in the range of 480–700 nm, CaO:Ce3 +,Na+ exhibits a strong yellow emission band located around 555 nm. The temperature-dependent luminescence behavior of this phosphor indicates that CaO:Ce3 +,Na+ exhibits better thermal stability than commercial YAG:Ce3 +.