Acute pulmonary thromboembolism (PTE), which carries a high mortality rate, is difficult to diagnose when it occurs intraoperatively. Therefore, patient prognosis depends on a prompt diagnosis by anesthesiologists. A 49-year-old woman underwent right lower extremity dissection due to a contusion of the right lower extremity caused by trauma. Eleven days after surgery, she underwent debridement for necrosis of the amputation wound. Intraoperatively, a drop in blood pressure and tachycardia were observed, and PTE was suspected based on a rapid deterioration in oxygen saturation and a drop in end-tidal carbon dioxide partial pressure. Transesophageal echocardiography (TEE) showed a thrombus filling the right pulmonary artery, and a diagnosis of PTE was made. The patient was treated using venoarterial extracorporeal membrane oxygenation, and thrombectomy was performed the next day to save her life. In this case, we were able to diagnose and treat the intraoperative acute PTE at an early stage. In addition, the appropriate choice of treatment saved the patient's life without complications.