Acute pulmonary thromboembolism (PTE) is life-threatening and difficult to diagnose. However, echocardiography can help diagnose and monitor PTE by visualizing the thrombus and assessing hemodynamic changes. Here we report the usefulness of transesophageal echocardiography (TEE) in a diagnosis of maternal PTE during cesarean delivery by showing a thromboembolus in pulmonary artery. In addition, TEE also prompted effective cardiopulmonary resuscitation for recurrent hemodynamic collapse due to a massive PTE, as well as rapid introduction of an extracorporeal membrane oxygenator to treat maternal hypoxia.