Administering anesthesia to patients with pheochromocytoma may cause an exacerbation of catecholamine secretion from the pheochromocytoma secondary to drug administration, stress, or manipulation of the tumor. We present a pediatric patient with undiagnosed multiple endocrine neoplasia type 2B (pheochromocytoma, thyroid carcinoma, and mucosal neuromas), initially diagnosed and treated for postviral myocarditis and cardiomyopathy, who presented for abdominal magnetic resonance imaging (MRI) under general anesthesia. Untreated cardiomyopathy poses an extra anesthesia mortality risk for patients with pheochromocytoma usually due to myocardial failure, myocardial infarction, or hypertensive hemorrhage into the myocardium or brain.