Mediastinal paragangliomas are exceedingly rare neuroendocrine tumors of chromaffin cell origin. They are rarely endocrinologically functional, but complications often arise due to mass effect within the mediastinal cavity. We present a case of a 67-year-old gentleman referred to our unit for excision of a large mediastinal mass, thought to be thymic in origin, but without confirmatory preoperative histological diagnosis. Intra-operatively it became clear that the tumor was intra-pericardial, originating from aortic tissue, mandating pericardectomy, and ascending aortic replacement on cardiopulmonary bypass for its complete excision. Histopathological evaluation later confirmed the mass to be an aorticopulmonary paraganglioma.