A 75-year-old male with a history of alcoholic liver cirrhosis, sigmoid colon cancer, and metastatic liver cancer was admitted to our institution with a complaint of a prickly feeling in his chest. On admission, a chest radiograph revealed a normal cardio-thoracic ratio of 47%. Echocardiography revealed pericardial effusion and blood chemical analyses revealed elevated C-reactive protein levels (14.7 mg/dL). On day 3, chest radiography revealed cardiomegaly with a cardio-thoracic ratio of 58% and protrusion of the left first arch. Contrast-enhanced chest computed tomography revealed a saccular aneurysm in the aortic arch with surrounding hematoma; thus, a ruptured thoracic aortic aneurysm was suspected. Emergency surgery was performed, which revealed a ruptured aortic aneurysm with extensive local inflammation. The diagnosis of an infected aortic rupture was therefore confirmed. The aneurysm and abscess were resected, followed by prosthetic graft replacement and omental packing. Histopathology of the resected aneurysm revealed gram-positive bacilli; and Listeria monocytogenes was confirmed as the causative organism by culture. Postoperative course was uneventful; on postoperative day 60, the patient was ambulatory and was discharged. Here we report the case of a male with a ruptured thoracic aortic aneurysm infected with L. monocytogenes.