Through-thickness distributions of the welding residual stresses were studied in the range of 50–100 mm thick plates by using finite-element modeling (FEM) and neutron diffraction measurements. In order to simulate the residual stresses through the thickness of the thick weld joints, this paper proposes a two-dimensional generalized plane strain (GPS) finite-element model coupled with the mixed work hardening model. The residual stress distributions show mostly asymmetric parabola profiles through the thickness of the welds and it is in good correlation with the neutron diffraction results. Both the heat input and plate thickness have little influence on the residual stress distributions due to the relatively large constraints of the thick specimen applied for each welding pass. A general formula has been suggested to evaluate the distributions of the through-thickness residual stresses in thick welds based on FEM and neutron diffraction experimental results.