Systemic side effects, including sepsis, due to bacille Calmette-Guérin treatment for carcinoma in situ in the bladder, are observed in 15% of the patients. In rare cases, patients developed systemic infections and mycotic aneurysms. In this case report, a 72-year-old man developed a mycotic aortic aneurysm, and the appropriate tuberculostatic drugs had no effect on his systemic infection. He was successfully treated surgically, replacing the affected aortic segment with an autologous venous graft, resulting in complete remission. A follow-up PET-CT three months later showed no sign of ongoing aortic infection.