A 76-year-old female presented with constipation and anorexia Computed tomography (CT) revealed a saccular aneurysm (35 mm in diameter) directly over the root of the celiac artery, and she was referred to our department and was admitted. Klebsiella pneumoniae was detected in blood culture. Although antibiotics were administered, the inflammatory response was not improved. On day 8 after hospitalization, CT revealed the aneurysm increased. Therefore, surgery was performed. Aneurysm was observed adjacent to the celiac artery. The excised aorta included the descending thoracic aorta and the superior mesenteric artery, and was replaced with a rifampicin-soaked Vasctec Gelweave 24 mm vascular graft with branches. After hemostasis, omental implantation was performed around the vascular graft. Before surgery, sufficient antibiotics administration is desirable to bring the infection under control. However, if infection is uncontrollable with progressive enlargement of the aneurysm, as in this case, surgery is unavoidable. A combination of treatments was successful.