A squeeze cast magnesium–aluminium–zinc alloy AZ31 was subjected to equal-channel angular pressing (ECAP) at 200°C up to four passes following route B_c. The grain size was reduced by a factor of about 100–200 through ECAP processing. The mechanical properties of as cast (non-pressed) and the ECAP-processed material were examined using compression tests from room temperature to 300°C. ECAP pressing resulted in a significant increase of the room temperature yield strength of the alloy. At elevated temperatures (200 and 300°C) an inverse dependence was found, i.e. the yield stress in the ECAP-processed specimens was lower than in the cast material. A recrystallized structure was formed only after four passes of ECAP. Dynamic recrystallization occurred during the deformation at elevated temperatures (300°C). Coarser recrystallized grains were formed in the specimen that had undergone four passes of ECAP. The strain imposed by ECAP influences the heterogeneity of the final microstructure of specimens after compression tests.