Numerous engineering components and structures require welding, including ships, automobiles, and many other manufactured products. Distortions and residual stresses created in welded joints can lead to adverse and destructive effects on structural integrity, service life, and visual appearance, and can produce significant dimensional inaccuracies. The ability to predict these effects accurately is, therefore, crucial for ensuring weld functionality and long service life. This study aims to examine the characteristics of welding deformation and residual stress in cruciform fillet welded joints using the FE software Simufact Welding. In the work, experimental measurements of temperature, deflection, and residual stress were used to verify the simulation models. The effect of plate thickness and welding sequence on welding deformation was examined through numerical simulations and experimental work. Additionally, the cause of angular distortion was explained using an FE model. An X-ray diffraction technique was adopted to record residual stress levels for the cruciform fillet welded joints. Reasonable agreement was found between the experimental measurements and the results obtained from the simulations.