The strength-ductility trade-off in magnesium alloys remains a critical challenge urgently requiring resolution in their engineering applications. In this study, both mechanical and corrosion properties are enhanced in extruded Mg-Y-Nd-Zr alloys by Sm addition. Sm promotes dynamic recrystallization, activates non-basal slip systems and weakens basal texture intensity, leading to the sub-grain lamellar structure and rare earth texture. The EWS2 alloy exhibits an outstanding combination of high yield strength (328 MPa) and ductility (15.1%). Furthermore, the fragmented second phases in the Sm-containing alloy are uniformly distributed, reducing the subsequent corrosion driving force after micro-galvanic corrosion and facilitating the growth of a more passivating and compact corrosion film. These combined effects contribute to the lowest degradation rate in the EWS2 alloy. This study demonstrates the correlation between microstructure and properties in Sm-containing WE series alloys, providing insights for the design of other high performance magnesium alloys.