Pheochromocytoma is an uncommon tumor in the pediatric population. Paraganglioma, or extra-adrenal pheochromocytoma, accounts for only a small fraction of pediatric pheochromocytomas, with most of these tumors presenting within the abdominal cavity. Herein the authors report the extremely rare case of a biochemically active paraganglioma presenting as a posterior mediastinal mass in an 8-year-old boy.