In a multilayered ceramic actuator structure, controlling the interface between the electrode and the ceramics is an essential technology for obtaining highly reliable ceramic actuators. The interface between Ag-Pd internal electrode and Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3(PNN-PT-PZ), and the grain boundary in PNN-PT-PZ ceramics, were studied using TEM and EDS. We found that Pb diffuses into the Ag-Pd electrode during firing. At the initial sintering stage, Ag in Ag-Pd seems to diffuse into the piezoelectric ceramics along the grain boundary. Ag diffused in the grain boundary is segregated, and a small amount of Ag diffuses into the grain of the ceramics at the medium sintering stage. When compared to the thick film process, the interfacial reaction between Ag-Pd and PNN-PT-PZ is promoted more in the cofiring process than the thick film process. This is because more Pb vapors diffuse into Ag-Pd in the cofiring process than the thick film process. The addition of Ag into PNN-PT-PZ decreases the dielectric constant and affects the dielectric loss slightly.