The mechanisms governing the microstructural evolution during friction stir welding of Monel at different heat inputs and the corresponding mechanical properties were investigated. In the low heat input condition, both continuous and discontinuous dynamic recrystallizations caused the formation of fine grains with an average grain size of 1.7 mu m and closely random texture. A high heat input condition resulted in larger average grain size of 23.5 mu m with shear texture by only the continuous dynamic recrystallization. Low heat input led to the simultaneous increase of strength and elongation. The origins of the tensile behavior of the joints have been discussed. (C) 2019 Elsevier B.V. All rights reserved.