We reported a case in a previously healthy 45-year-old woman of spontaneous rupture of the left external iliac vein, which was revealed as a phlegmasia cerulea dolens with acute lower limb ischemia. A tear on the anterior surface of the vein was discovered during an emergency laparotomy, and the rent was repaired successfully. Twenty-four hours later, the leg swelling increased, and at the reexploration, the common iliac vein was found to be occluded by an organized thrombus as the result of a well-endothelialized membranous band (Cockett or May-Turner syndrome). A Palma-Dale operation (crossover saphenous bypass grafting) was performed secondarily. The swelling in the leg diminished slowly, and the patient was discharged 10 days later with an oral anticoagulant therapy and elastic stockings.