The dielectric and piezoelectric properties of SrBi2-xSmxNb2O9 (x=0, 0.05, 0.1, 0.2, 0.3, and 0.4) ceramics were investigated. SrBi2-xSmxNb2O9 ceramics were synthesized by the conventional solid-state reaction sintering method. An X-ray diffraction measurement indicated that a single-phase-layered perovskite was obtained for all compositions. The substitution of Sm3+ for Bi3+ in the Bi2O2 layers induced a relaxor behavior of frequency dispersion for SrBi2-xSmxNb2O9. The Raman spectra of SrBi2-xSmxNb2O9 revealed that the decrease in T-m could be attributed to smaller structural distortion of NbO6 octahedra that is induced by the substitution of Sm3+ for Bi3+. SrBi2-xSmxNb2O9 (x <= 0.2) ceramics are suitable for fine tolerance resonator applications because the Sm3+ doping in Bi2O2 layers can improve the temperature coefficient of resonance frequency.