Abstract: The 3D residual stresses in the friction stir and tungsten inert gas welded 2219 aluminum alloy sheets were characterized using neutron diffraction. The results show that residual stress is larger in longitudinal direction after welding process. The magnitude of the residual stress in friction stir welded sheet is generally smaller than that in the tungsten inert gas welded sheet. The maximum tensile stress of friction stir welded sheet is 101 MPa, which is smaller than that of tungsten inert gas welded stress of 174 MPa. Friction stir welded sheet tensile peaks show at sides of the tool edge, and the tensile residual stress on the advancing side is higher than that on the retreating side. Tungsten inert gas welded stress residual stress peaks show at the sides of welding zone. Residual stress distributions obtained by neutron diffraction will be used to optimize the welding process and predict the lifespan of 2219 aluminum alloy.