Popliteal artery entrapment syndrome is recognized as a cause of claudication and arterial occlusion in young patients. Aneurysmal degeneration is a reported but rare complication. We present the case of a young male patient with large bilateral popliteal aneurysms due to symptomatic anatomic entrapment. The left aneurysm was acutely thrombosed, and urgent bypass surgery was required. The contralateral aneurysm was resected by a posterior approach and replaced with an autologous vein graft. Type IV popliteal entrapment by a fibrous band independent of the gastrocnemius muscle was diagnosed during surgery and divided. Early detection of popliteal entrapment is highly important to prevent the development of this serious complication.