Aortitis is an inflammatory condition that can be due to numerous causes. It is a diagnostic quandary because it commonly shows similar clinical, pathologic, and aortographic features independently of the etiology. A case of aortitis, possibly secondary to bacterial endocarditis, initially misdiagnosed as an atherosclerotic aortic ulcer and managed with an endoprosthesis is presented. On the fourth postoperative day, the patient presented with fever and worsening abdominal pain, which was later diagnosed as infectious aortitis. It required débridement and replacement of the infrarenal aorta with a cadaveric cryopreserved allograft. This case emphasizes the need for early diagnosis and aggressive therapy to avoid life-threatening sequelae.