Abstract: To mitigate the adverse effects of web openings on the structural load-bearing performance of castellated beams, a type of castellated beam with stamped and hemmed web openings, referred to as the edge-stiffened castellated beam (CBE), was investigated. Static load tests were conducted on one unstiffened and three edge-stiffened castellated beams with long circular openings to study the mechanical behavior and failure mechanisms of CBE under different parameters. A refined finite element model considering the cold-bending effect of hemming was established and validated against the experimental results. A parametric analysis was then performed to study the enhancing effect of the hemming process on the flexural performance and to analyze the influence of opening ratio, hole spacing, and web thickness on the flexural bearing capacity of CBE. The results indicate that hemming significantly improves the local stability of the web. The ultimate bearing capacity of the specimens with a flange edge increased by 23.4% compared to the unstiffened specimens, and the strengthening effect is more pronounced under large opening ratios. The distance-to-height ratio has a minor impact on the bearing capacity, but hemming plays a role in suppressing local buckling when this ratio is small. The flexural bearing capacity of CBE increases linearly with the decrease of the web height-to-thickness ratio, indicating that hemming can serve as an effective reinforcement measure for thin and slender webs. Based on the effective section method and the theory of compression-bending lattice members, a calculation method for the flexural bearing capacity of CBE with long circular openings was proposed. The calculation results are in good agreement with both experimental and finite element results, providing a theoretical basis for the engineering design and application of such members.