We report a case of a 10-year-old male patient with pulmonary artery aneurysm (PAA) caused by infective endarteritis of the pulmonary artery attributed to patent ductus arteriosus. He was found to have patent ductus arteriosus at the age of 2, but he was not treated because of the absence of symptoms and normal physical development. He sought medical attention for fever and cough in August 2022. Echocardiography showed pulmonary artery aneurysm, intrapulmonary artery bulge, patent ductus arteriosus, and pericardial effusion. Contrast-enhanced CT showed pulmonary artery aneurysm, patent ductus arteriosus, and a slight compression of the left main bronchus. Surgery was performed to reconstruct the main pulmonary trunk and repair the ductus arteriosus in November 2022. The surgical outcomes were satisfactory.