CuO-added (1-x)KNbO3-x mol%BaZrO3 ceramics with 0.0x7.0 were sintered at 960 degrees C. Large double polarization vs electric field (P-E) and sprout-shaped strain vs electric field (S-E) hysteresis curves were obtained from the specimens with x2.0. They exhibited large polarizing electric fields (E-P) owing to the presence of a large number of defect dipoles (P(D)s) that formed between Cu2+ ions and oxygen vacancies. Small double P-E hysteresis curves were observed for the specimens with x3.0 with reduced E-P because of the decreased number of P(D)s and the presence of a polymorphic phase structure containing both orthorhombic and pseudocubic structures. In particular, the specimen with x=5.0 exhibited a large strain of 0.16% at 8.0kV/mm with a small E-P of 1.2kV/mm and good fatigue property: this specimen maintained a strain of 0.13% at 6.0kV/mm after 10(6) cycles of 3.0kV/mm.