Abstract Two novel Eu2+-activated phosphors in the Na–Sc–Si–O system were developed in this study, NaScSi2O6:Eu and Na3ScSi3O9:Eu. NaScSi2O6:Eu2+ showed yellow emission with a peak at 555nm under excitation at 220–430nm. When flux-treatment was performed for NaScSi2O6:Eu2+, we found the existence of a new phase. We then succeeded in synthesis of a high-purity sample of this new compound by a parallel solution synthesis method. It was revealed that the new phase was Na3ScSi3O9 with isostructure to Na3YSi3O9, and Eu2+-activated Na3ScSi3O9 exhibited photoluminescence. Na3ScSi3O9:Eu showed green emission with a peak at 530nm and a corresponding broad excitation band up to 500nm. However, photoluminescence of Eu2+ was negligible for Na3YSi3O9:Eu because of the stabilization of Eu3+ at the Y3+ site.