(111)-oriented epitaxial (1 − x)Bi(Mg1/2Ti1/2)O3–xBi(Zn1/2Ti1/2)O3 solid solution films were grown on (111)cSrRuO3/(111)SrTiO3 substrates by pulsed laser deposition, and their crystal structure and electrical properties were characterized. The solid solution films consisted of a perovskite single phase in the x range of 0–0.93. The coexistence region of rhombohedral and tetragonal phases was observed in the x range of 0.18–0.60, which differed from reported data for the powders synthesized at high temperatures and high pressures. The polarization–electric field hysteresis loops originating from ferroelectricity were observed at room temperature and 1 kHz in the x range of 0–0.33, and the remanent polarization monotonously decreased with increasing x. The relative dielectric constant measured at room temperature and 100 kHz and the apparent piezoelectric constant evaluated by piezoresponse force microscopy at room temperature and 5 Hz were maximum at approximately x = 0.14. These results suggest that these tendencies of the electrical and electromechanical properties were related to the volume fractions of the constituent phases in the solid solution films.