A schwannoma is a benign neoplasm originating from the Schwann cells of the neural sheath. The most common type of benign schwannomas is the acoustic neuroma presenting with deafness. We report a rare case of schwannoma mimicking an adrenal mass. A 66-year-old woman was diagnosed with an adrenal incidentaloma measuring 10 cm in length on a health checkup. The hormonal study revealed that the adrenal mass was non-functioning. Due to a high risk of adrenal malignancy, a retroperitoneal mass excision, distal pancreatectomy, splenectomy, wedge resection of stomach, and left adrenalectomy were conducted. The subsequent histopathologic examination revealed it to be a benign schwannoma.