Adventitial cystic disease (ACD) is an uncommon and rare vascular entity characterized by a highly viscous and mucinous cyst located in the adventitia of an artery. Although first described in the external iliac artery, the disease is more frequently sited in the popliteal artery. ACD characteristically occurs in young adults, mostly male, with intermittent claudication as the initial presenting symptom. As the cyst enlarges, it leads to vascular compression with stenosis or occlusion. Because cystic formation of the popliteal artery is uncommon, the disease is often unrecognized. We report a case of popliteal artery ACD in a 54-year-old woman who was successfully treated surgically.