The eco-friendly thermoelectric material SnTe has recently gained immense attention due to its excellent thermoelectric properties and potential. However, its thermoelectric properties are limited by the inherent high carrier concentration (low Seebeck coefficient) and high thermal conductivity. Herein, we further introduce rare-earth element Y on top of the conventional Cu alloying to more effectively modulate its microstructure and thermal transport properties. The experimental results reveal that Y doping gives rise to band convergence, endowing Sn 1−x Y x Te-5%Cu 2 Te with an increased power factor of ∼22.14 μW cm −1 K −2 . Meanwhile, the introduced abundant Y/ Y 2 Te 3 multiscale composite nanostructures in the matrix greatly enhance phonon scattering, resulting in an ultra-low lattice thermal conductivity of ∼0.43 W m −1 K −1 . Consequently, these combined effects resulted in a peak ZT value of 1.27 at 823 K in Sn 0.97 Y 0.03 Te-5%Cu 2 Te. An enhancement of nearly 217% is achieved compared to pristine SnTe, which greatly improves the thermoelectric properties of SnTe-based materials.