Pulmonary artery sarcoma is an extremely uncommon malignancy with a poor prognosis. It is often difficult to distinguish it from pulmonary thromboembolic disease because of nonspecific signs and symptoms as well as similar imaging findings. We present a 46-year-old man who had initially been diagnosed with presumed asthma that later proved to be pulmonary artery sarcoma. The patient was evaluated with multi-modality imaging studies which showed a mass in the pulmonary artery, its extension, mobility and invasion, and attachment to the artery wall. Pulmonary artery mass was excised and pulmonary artery endarterectomy was performed. The histopathological diagnosis was undifferentiated sarcoma with pleomorphic morphology.