The Mg micropowder was mixed and ball milled with ceramic nanoparticles. The material was compacted and then hot extruded. Samples have been deformed in tensile as well as compression tests at temperatures between 20 and 300 °C at a constant initial strain rate. The flow stress is significantly influenced by temperature. The yield stress and maximum stress decrease with increasing temperature. Stress strain curves obtained at lower temperatures in tensile tests substantially differ from ones estimated in compression. Stress relaxation tests were conducted in order to find the internal stress as well as to identify possible thermally activated process(-es).