A thirty-three-year-old male with malignant hemangiopericytoma of the right ventricular outflow tract and the pulmonary artery associated with pseudoaneurysm formation at the latter is presented. Contrast computed tomography was helpful in diagnosing the pseudoaneurysm of the pulmonary artery. The positional change of the murmur, with a tumor plop caused by the pedunculated tumor of the right ventricular outflow tract, was detected.