Because the adrenal glands are common locations for metastases, pheochromocytoma is frequently misdiagnosed as adrenal metastasis in patients with a history of cancer. An incidental adrenal mass was detected during an abdominal computed tomography (CT) scan performed to stage the nasopharyngeal carcinoma in a 35-year-old male patient. The features of an adrenal mass on the CT, magnetic resonance imaging (MRI), and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) were thought to show adrenal metastasis. However, the patient did not complain about flushing, palpitation, headache or excessive sweating. His blood pressure was 132/74 mmHg, and his pulse rate was 82 bpm. A pheochromocytoma was found during a biochemical diagnosis that evaluated the catecholamine in urine collected over a 24- hour period. The urine had elevated urinary adrenaline, metanephrine, and vanillylmandelic. An I123 MIBG scan showed avid tracer uptake in the right adrenal mass with no evidence of abnormal uptake elsewhere. A right adrenalectomy operation was performed and a diagnosis of pheochromocytoma was confirmed histopathologically. Incidental adrenal masses detected in the presence history of cancer should always be subjected to hormonal evaluation. Although patients may be asymptomatic, the probability of incidental pheochromocytoma should not be ignored.