Welding-induced buckling is a special type of welding distortion occurring during thin plate butt welding and was investigated using both experimental and computational approaches for this benchmark investigation. In addition, the characteristic parameter and its magnitude for the occurrence of welding-induced buckling were also presented. Fundamental theories of the inherent deformation, finite strains, and eigenvalues of the structure stiffness matrix were considered to investigate welding-induced buckling. A series of experiments on thin plate butt welding with different heat inputs were conducted, and buckling behavior was observed from the deformed shape and the distribution of out-of-plane welding distortion. Transient nonlinear thermal elastic–plastic finite element (TEP FE) and elastic finite element (FE) analyses were conducted to predict welding-induced buckling, and the results were in good agreement with the measurement data. Criteria for the occurrence of welding-induced buckling were proposed and discussed. Inherent deformation was considered as a characteristic parameter of buckling behavior during welding, and its critical magnitude was calculated using a loading incremental method and eigenvalue analysis with good agreement.