Corrosion-induced degradation of steel girder ends in bridge structures poses a significant challenge, notably compromising their shear load-carrying capacity. This experimental investigation aims to elucidate the intricate relationship between corrosion severity and the resulting reduction in shear strength. A controlled experimental setup involving five specimens, subjected to varying degrees of corrosion severity, was employed. The study examines the structural impact of corrosion on girder ends, particularly focusing on severe corrosion near supports. Observations reveal alterations in stresses transferred from the web to the lower flange, which is interrupted due to corrosion in the web’s lower part. Furthermore, the study investigates the mechanisms driving the reduction in shear buckling strength and explores the effects of corrosion on compression band boundary conditions and the corresponding post-buckling strength of the corroded panels. Finally, the study assesses the integrity of heavily corroded panels, aiming to provide insights into the extent of shear strength decrease and its implications for residual strength estimation and future maintenance strategies.