An incidental adrenal mass is a common finding on cross-sectional imaging, with most of these lesions being benign adenomas. Indications for adrenalectomy turn on the likelihood that a mass is malignant or whether it exhibits metabolic activity. Modern imaging is considered highly accurate in differentiating adrenal adenomas from other adrenal pathology. We present a case of a 5-cm adrenal lesion with computed tomography washout characteristics consistent with a benign adenoma, which proved upon resection to be an adrenocortical carcinoma.