The dynamic shear deformation behaviour and fracture characteristics of Al-Sc alloy are studied using a split-Hopkinson torsional bar at shear strain rates of 800 s-1, 1800 s-1 and 2800 s-1 and temperatures of -150°C, 25°C and 300°C. The experimental results indicate that the shear strain, shear strain rate and temperature all have a significant influence on the mechanical properties of the alloy. The fracture surfaces of the gauge length section of the deformed specimen are twisted into band-like features as a result of intensive localized shear deformation. The width and microhardness of the shear band changes with strain rate and temperature as a result of different work hardening effects. Specimen fracture initiates at the Al3Sc precipitate/matrix interface. The presence of precipitates accelerates the dynamic shear fracture formation via microcracking.