True aneurysms of the profunda femoris artery are extremely rare in comparison to pseudoaneurysms of the same artery. In most cases they are accompanied by aneurysms of the abdominal aorta or peripheral vessels. The most common reason for aneurysmic dilatation of vessels is a generalized vascular degenerative process. An isolated true aneurysm of the profunda femoris artery due to atherosclerosis is markedly unusual. These aneurysms have a high incidence of complication; therefore surgical management is mandatory for all diagnosed cases regardless of whether they are symptomatic or not. We describe a case of a 73-year-old man with a large isolated atherosclerotic aneurysm of the profunda femoris artery. He presented with an enlarging, progressively debilitating mass in his upper thigh. Ultrasound and computed tomography-angiography demonstrated a 15 x 14 cm large aneurysm of the profunda femoris artery. The patient was successfully treated by aneurysm neck ligation and sac decompression.