Unimorph cantilevers are made from 0.5BaTiO3‐0.5Sm2O3 (BTO‐SmO) self‐assembled vertical heteroepitaxial nanocomposite thin films, grown by PLD on (001) SrTiO3 single crystal substrates. The films remain piezoelectric up to at least 250 °C without losing any actuation. The longitudinal piezoelectric coefficient, d33, is ≈45 to 50 pm V−1 measured from room temperature to 250 °C. The transverse piezoelectric coefficient, d31, a key parameter of actuator performance, exceeds PZT (Pb1–xZrxTiO3) films at >200 pm V−1. Since the d31 coefficient was found to be positive, this opens up exciting new applications opportunities. The possible reasons for d31 > 0 are discussed in the light of 3D strain control in the nanocomposites.