The present study has expounded the effect of high temperatures on the tensile deformation of AZ31 magnesium alloy processed through a single-pass of friction stir processing (FSP). The major operation parameters, namely rotation speed and traverse speed of the FSP tool, were varied which led to extensive dynamic recrystallization (DRX) in the stir zone (SZ) engendering maximum grain refinement of about 63% as compared to the base metal. The lowest average grain size ∼ 5.66 μm was attained after a single FSP pass. Optical microscopy (OM) was followed by the uniaxial tensile tests at three different temperatures of 350, 400 and 450 ºC at a constant strain rate of 1.3 × 10−3/s. As the deformation temperature was raised, the flow stress reduced and led to appreciable increments in the processed material’s tensile elongations. The maximal elongation to fracture of 160% was observed in the friction stir processed (FSPed) sample possessing the finest grains.