Determination of microstructural and mechanical response to real-world loading conditions is imperative for the development of accurate models to predict the failure behavior of structural materials. The dynamic behavior of magnesium alloys is of particular interest to structural industries as lightweight materials must be able to withstand high impact loading. This study examines the influence of dynamic strain rate on the deformation behavior of a polycrystalline, hot-rolled AZ31 Mg alloy under varying stress triaxialities. The high strain rate testing results indicate that an increase in triaxiality leads to a transition in the deformation mechanisms. Subsequent characterization of microstructure and fracture surfaces were correlated to the mechanical response observed. Finally, these findings provide critical insights into the role of stress-state on dynamic behavior of an AZ31 alloy.