The hot compression deformation of an Mg–2.54Nd–0.26Zn–0.32Zr cast alloy was investigated in the 25–400°C temperature range at initial strain rates from 10 −4 s −1 to 10 −2 s −1. It was found that strain rate has little effect on true stress when the material was compressed below 250°C. Above this temperature, high strain rates resulted in an increased true stress. The average strain rate sensitivity exponent at higher temperature (300–400°C) was determined to be 0.24 and the calculated activation energy was 185 kJ · mol −1, which is higher than that of lattice self diffusion of pure Mg. The constitutive equation was established and the Zener-Hollomon parameter was calculated as a function of peak stress. The microstructure of a sample tested at 300°C was analyzed by optical microscopy.