We report a rare case of vascular graft-associated aneurysmal angiosarcoma by 18 F-Fluorodeoxyglucose (FDG) positron emission tomography (PET). An 81-year-old male patient, with a prior history of graft interposition 1 year previously, was referred to 18 F-FDG-PET because of an inflammatory syndrome of unknown origin. FDG-PET images revealed a particular pattern of intense circular uptake within the arterial wall (SUVmax ¼ 10) in a popliteal aneurysm and, additionally, a large hypermetabolic mass centered by the graft. Remote hypermetabolisms in lung nodules and pleural thickenings were also detected. The diagnosis of angiosarcoma was ascertained through histopathological analysis of surgical samples. Development of an aneurysmal angiosarcoma at the site of a vascular graft is a rare entity, often misdiagnosed. 18 F-FDG-PET appears to be useful in its detection with a PET pattern of intense circular uptake within the arterial wall. Such finding should lead to the search for distant metastasis.