The elastic, piezoelectric, and dielectric properties of [001] c and [011] c poled 0.33Pb(In 1/2 Nb 1/2 )O 3 –0.38Pb(Mg 1/3 Nb 2/3 )O 3 –0.29PbTiO 3 single crystals have been fully characterized at room temperature, and the temperature and frequency dependence of the dielectric susceptibility ε 33 were also measured. The depoling temperature of this crystal is more than 20°C higher than that of the corresponding binary 0.71Pb(Mg 1/3 Nb 2/3 )O 3 –0.29PbTiO 3 system. From the measured P–E hysteresis loops, the coercive fields along [001] c and [011] c directions have been determined to be 6.0kV/cm and 6.6kV/cm, respectively, which indicate that these domain engineered ternary relaxor-based ferroelectric single crystals are excellent candidates for high-power applications.