We report a rare case of spontaneous thrombosis of a ruptured deep femoral artery aneurysm. An 85-year-old man presented two days after onset of acute swelling and pain in the left groin. Computed tomography demonstrated rupture of a deep femoral artery aneurysm and thrombosis of the aneurysm. After 1 month of observation, surgical intervention was performed as the local pain persisted. Opening of the aneurysm sac confirmed that thrombosis was complete. Simple ligation and drainage of the aneurysmal sac was performed. His postoperative course was uneventful.