Pheochromocytoma is a rare neuroendocrine tumor arising from the medulla of the adrenal glands, which causes an overproduction of catecholamines. The common symptoms are headache, palpitations, and sweating; however, various other clinical manifestations might also be present. Accurate diagnosis of pheochromocytoma is important because surgical treatment is usually successful, and associated clinical problems are reversible if treated early. A 49-year-old man with a history of uncontrolled hypertension and diabetes mellitus presented with chest pain, fever, and sweating. His liver function tests and white blood cell counts were markedly increased and his echocardiography results suggested stress-induced cardiomyopathy. His abdominal computed tomography showed a 5x5-cm-sized tumor in the left adrenal gland, and laboratory tests confirmed catecholamine overproduction. After surgical resection of the left adrenal gland, his liver function tests and white blood cell counts normalized, and echocardiography showed normal cardiac function. Moreover, his previous antihypertensive regimen was deescalated, and his previously uncontrolled blood glucose levels normalized without medication.