The origin of the significantly large piezoelectricity and ferroelectricity was investigated in the 0.67BiFeO3–0.33BaTiO3 ceramics. The crystal structure of 0.67BiFeO3–0.33BaTiO3, identified using the Rietveld method, suggested a cubic structure at 950 K and a rhombohedral structure at 300 K with small lattice distortion 89.94(4)°, which is close to 90° of cubic structure. Despite the small lattice distortion at 300 K, significantly large piezoelectricity and ferroelectricity was observed in the 0.67BiFeO3–0.33BaTiO3, which is associated Bi ion off-centering. The Bi3+ ions were off-centered from the corner of the Ba2+ position along the 〈100〉 directions at 300 K, occupying three equivalent neighboring sites in the [100], [010], and [001] directions. The occupancies of Bi ions could be changed, and partially ordered along the applied electric field direction. The off-centered Bi ions are attributed to the ferroelectricity and piezoelectricity in non-centrosymmetry structure with a small lattice distortion, i.e., pseudo-cubic structure, due to partial ordering under the electric field.