The mechanism of improvement of resistance degradation in Y-doped BaTiO 3 based multilayer ceramic capacitors (MLCCs) with Ni electrodes has been studied using electrical measurement techniques, minor phase identification and the measurement of oxygen vacancy concentration. Admittance spectroscopy and thermally stimulated current measurements show the relaxation due to barium vacancy states caused by Y doping. The minor phase identification by XRD indicated those Y 3 + substitutes for perovskite A-site. Oxygen vacancy concentration measurement indicated that Y decreases the oxygen ion vacancy concentration in BaTiO 3 . These results suggest that Y 3 + acts as a donor and creates barium vacancies, which compensate for the oxygen vacancies and thereby improve the resistance degradation.