A 59-year-old woman was admitted to our hospital because of general fatigue and dyspnea. She suffered hypoxia and right heart failure because of pulmonary hypertension. However, a chest contrast-enhanced computed tomography (CT) showed no thrombus in pulmonary artery, but abdominal CT revealed intrapelvic tumors. Within a 5-h duration, she died of cardiopulmonary arrest resulting from rapid progression of respiratory and right heart failure. An autopsy revealed ovarian cancer and widespread tumor embolisms, along with fibrocellular intimal proliferation and thrombus formation in pulmonary arterioles. No tumor cells were detected in any other organs; thus we thought the primary tumor was most likely ovarian cancer, and the patient was diagnosed as having pulmonary tumor thrombotic microangiopathy (PTTM) caused by ovarian cancer. As in this case, if we have a patient with pulmonary hypertension and no embolism in the proximal pulmonary arteries on the enhanced CT, we should consider PTTM as the differential diagnosis.