A fatal case of late-onset graft infection of the thoracic aorta due to group C beta-hemolytic streptococcus is described. A 37-year-old male patient, who had a history of total aortic arch replacement for acute aortic dissection 8 years before, was admitted to the department. He suffered from toxic shock syndrome, disseminated intravascular coagulation (DIC), and acute renal failure. Group C beta-hemolytic streptococcus was detected from his blood; however, echocardiography, computed tomography (CT), and magnetic resonance imaging (MRI) failed to detect the focus of the infection. In spite of intensive care, including antibiotic therapy, artificial ventilation, and continuous hemodiafiltration, he died on the 18th day of hospitalization. Autopsy revealed that a small abscess was present at the proximal anastomotic segments of the patient's graft. A bite inflicted by his dog, 14 days before admission, was suspected to be the source of this bacterium. A rare case of graft infection of thoracic aorta in terms of causative organism, long period from graft replacement to graft infection, and site of infection is presented and discussed.