In this study, (Zn,Mg)TiO3+x+Bi2O3+Sb2O5 multilayer ceramic capacitors (MLCCs) with different proportions of a silver (Ag)-palladium (Pd) mixture acting as the inner electrode were sintered at 925 degrees C for 2 h to evaluate the effect of the inner electrode on reliability. The main results reveal that the lifetime is inversely proportional to the Ag content in the Ag/Pd inner electrode. Ag diffusion into the (Zn,Mg)TiO3+x+Bi2O3+Sb2O5 MLCC during cofiring at 925 degrees C for 2 h and Ag migration at 140 degrees C against 200 V are both responsible for the short lifetime of the (Zn,Mg)TiO3+x+Bi2O3+Sb2O5 MLCC, particularly the latter factor. A Bi,Sb-rich secondary phase was present at the triple junction and a small amount of Ag was detected from the second phase for a (Zn,Mg)TiO3+x+Bi2O3+Sb2O5 MLCC with a high Ag content in the inner electrode of Ag/Pd = 99/01. However, this was not the case with a low Ag content in the inner electrode of Ag/Pd = 90/10. This means that the Bi,Sb-rich second phase plays an important role in determining the degradation of insulation resistance due to the excessive formation of oxygen vacancies from the reaction of Ag+ for Bi3+ or Sb5+ substitution to lower the activation energy of the (Zn,Mg)TiO3+Bi2O3+Sb2O5 dielectrics and to enhance markedly the effect of Ag migration.