Pulmonary artery aneurysm is rarely seen in clinical practice. It has been reported to develop in patients due to several underlying etiologies. However, the natural history is not yet defined, and management remains controversial. We report a case of giant main pulmonary artery aneurysm 6.06 cm in diameter in an asymptomatic 75-year-old male who has an incidental abnormal chest x-ray for preoperative evaluation as management of benign prostatic hypertrophy. The patient was managed conservatively. He was discharged home in good general condition to be followed up by echocardiography every 6 months. We conclude that pulmonary artery aneurysm can reach a massive size with no apparent symptoms. The treatment can therefore be conservative as no clear guidelines to support interventional management, particularly in the absence of pulmonary hypertension.