The microstructure and mechanical properties of an indirect-extruded Mg–8Sn–1Al–1Zn (TAZ811) alloy were investigated and compared with those of a commercial Mg–3Al–1Zn (AZ31) alloy. In the extruded condition, the TAZ811 alloy shows a much smaller grain size but a stronger basal texture than the AZ31 alloy. In addition, the TAZ811 alloy contains fine Mg 2 Sn particles in the microstructure, whereas the AZ31 alloy reveals relatively coarse and sparse Al–Mn particles. The TAZ811 alloy showed tensile and compressive strengthening as well as a reduction in yield asymmetry between tension and compression, which is mainly due to grain refinement and the presence of fine Mg 2 Sn particles.