A 60-year-old male with exertional dyspnea was referred to our hospital. Right pulmonary artery stenosis due to external compression by a calcified band was diagnosed by echocardiography, computed tomography, and magnetic resonance imaging. Percutaneous transluminal angioplasty was conducted in vain due to vascular recoil and failure of stent delivery. Pulmonary bypass grafting was performed successfully. The surgery indicated a probable etiology of chronic pericarditis. This is an extremely rare case of adult pulmonary artery stenosis without a known history of congenital disease, constrictive pericarditis, tuberculosis, or surgery.