Magnesium alloy EZ10(Mg-RE-Zn) was deformed in tension at temperatures from 20 up to 520 °C. A rapid decrease of the yield and tensile strength with temperature was observed at temperatures higher than 300 °C. On the other hand, ductility of samples rapidly increased in the same temperature range. Light microscopy and scanning electron microscopy was used to reveal the reason for these behaviours. Intermetallic particles in grain boundaries are responsible for excellent mechanical properties at lower temperatures. Diffusional processes occurring at temperatures higher than 300 °C significantly influenced the deformation mechanism as well as the fracture character. Magnesium alloy EZ10 (Mg-RE-Zn) was deformed in tension from 20 up to 520 ° C. A rapid decrease of yield and tensile strength with temperature was observed at temperatures higher than 300 ° C. On the other hand, ductility of samples rapidly increased in the same temperature range. Light microscopy and scanning electron microscopy was used to reveal the reason for these behaviors. ° C significant influenced the deformation mechanism as well as the fracture character.