Pulmonary artery sarcoma is an uncommon neoplasm, and its clinical and radiological presentation usually simulates chronic thromboembolic disease. We present the case of a 77-year-old woman admitted with dyspnea, chest pain, and hemoptysis. A chest computed tomographic scan showed moderate right-sided pleural effusion and a saccular dilatation of the interlobar portion of the right pulmonary artery, which was filled with contrast and surrounded by an irregular soft-tissue attenuation mass, suggesting a ruptured pulmonary artery aneurysm. The patient was operated on. Intraoperatively, a pseudoaneurysm and a solid mass were identified within the oblique fissure around the interlobar artery. Therefore, a right pneumonectomy was performed. Definitive pathologic examination was consistent with pulmonary artery sarcoma. The patient had a good outcome and is free of disease 2 years after surgery.