The influence of the microstructural parameters on the extrinsic contributions to the electromechanical behavior of samarium modified lead titanate piezoceramics is studied. A complete structural, compositional and microstructural characterization has been carried out to this purpose.The electromechanical coupling factors k p and k 3 1 show strong dependence on the microstructure. There is not any important microstructural dependence of the electromechanical properties related to resonance modes for which vibration takes place in a direction parallel to the polarization. Evolution with the poling field of the dielectric permittivity and mechanical parameters is well correlated with simultaneous changes in the porosity content and the grain size, whereas dielectric losses depend as well on microstructural factors at a finer scale. Knowledge of the temperature behavior of the planar electromechanical coupling factor is needed to fully understand its variations compared with other modified lead titanate ceramics.