The pitfall of percutaneous cardiopulmonary support (PCPS), which is thought to be useful for the detection of massive pulmonary emboli in patients, was investigated. A case of massive pulmonary embolism occurring 9 days after repair of the left Achilles tendon in a 31-year-old woman is described. Preoperatively, the thrombi in the right atrium and between the left popliteal vein and soleus muscle vein, as well as a massive pulmonary emboli, were detected. Despite using PCPS, it was difficult to maintain arterial pressure because of the outflow cannular occlusion caused by the floating thrombus in the right atrium, and so therefore the patient became hemodynamically unstable. After the removal of the thrombus and after a cardiopulmonary bypass was established, a pulmonary embolectomy was performed.