A 79-year-old man with appetite loss and nausea for 1 month was admitted to our hospital. His thoracic aortic aneurysm had gradually increased in size due to perigraft endoleak after the previous aneurysm repair surgery. Although he showed no hematemesis, melena, or a fever, gastrointestinal endoscopy and contrast-enhanced computed tomography (CT) revealed an aortoesophageal fistula (AEF). He developed septic shock due to a perigraft abscess and eventually died, although aortic graft replacement and esophageal transection were performed. Clinical suspicion is the most important factor for obtaining an accurate diagnosis and improving the prognosis in cases of AEF.