Symptomatic presentation of ductal arteriosus aneurysm is usually a consequence of associated complications, including thromboembolism, infection, and compression of adjacent structures. In this case report, we present a thrombosed ductal aneurysm that developed antenatally with further postnatal progression of the thrombus and complete occlusion of the left pulmonary artery. Urgent surgical thrombectomy was successful and the post-operative course was uneventful.