The paper describes a case of IgG4-related chronic periaortitis in a 56-year-old man. Computed tomography revealed stenosis of the abdominal aorta and both common iliac arteries due to calcified atherosclerotic plaques, in this connection, bifurcation aorta-common femoral bypass surgery was performed. Intraoperatively, a solid retroperitoneal mass intimately connected with the walls of vessels was revealed in the retroperitoneal space around the aorta and iliac arteries. Histological examination ascertained rough fibrous connective tissue growth, a marked lymphoplasmacytic infiltration with an admixture of eosinophils, and formation of lymphoid follicles with germinal centers. Immunohistochemical examination revealed the plasma cell expression of CD20, IgG, IgG4, and kappa and lambda light chains in the inflammatory infiltrate. Because of active immune inflammation, further conservative therapy was recommended.