SrSnO3 phosphor powders were synthesized with two different contents of activator ions Eu3+ and Tb3+ using the solid-state reaction method. The structural, morphological, and optical properties of the phosphors were investigated using Xray diffractometry, field-emission scanning electron microscopy, and fluorescence spectrophotometry, respectively. All the phosphors showed a cubic structure, irrespective of the type and the content ratio of activator ions. For Eu3+-doped SrSnO3 phosphors, the intensity of the 620 nm red emission spectrum resulting from the 5D0→ 7F2 transition of Eu3+ was stronger than that of the 595 nm orange emission signal due to the 5D0→ 7F1 transition in the range 0.01-0.05 mol of Eu3+, but the ratio of the intensity was reversed in the range 0.10-0.20 mol of Eu3+. The variation in the emission intensity indicates that the site symmetry of the Eu3+ ions around the host crystal was changed from non-inversion symmetry to inversion. For the Tb3+-doped SrSnO3 phosphors under excitation at 281 nm, one strong green emission band at 550 nm and several weak bands were observed. These results suggest that the optimum red and green emission signals can be realized when the activator ion content for Eu3+- or Tb3+-doped SrSnO3 phosphors is 0.20 mol and 0.15 mol, respectively.