OBJECTIVE To recognize that benign adrenal adenomas can co-secrete excess aldosterone and cortisol, which can change clinical management. METHODS We reviewed the clinical and histological features of an adrenal tumor co-secreting aldosterone and cortisol in a patient. Biochemical testing as well as postoperative immunohistochemistry was carried out on tissue samples for assessing enzymes involved in steroidogenesis. RESULTS A patient presented with hypertension, hypokalemia, and symptoms related to hypercortisolism. The case demonstrated suppressed renin concentrations with an elevated aldosterone:renin ratio, abnormal dexamethasone suppression test results, and elevated midnight salivary cortisol concentrations. The patient had a right adrenal nodule with autonomous cortisol production and interval growth. Right adrenalectomy was carried out. Postoperatively, the patient tolerated the surgery, but he was placed on a short course of steroid replacement given a subnormal postoperative serum cortisol concentration. Long-term follow-up of the patient showed that his blood pressure and glucose levels had improved. Histopathology slides showed positive staining for 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase, and 21 hydroxylase. CONCLUSIONS In addition to the clinical manifestations and laboratory values, the presence of these enzymes in this type of tumor provides support that the tumor in this patient was able to produce mineralocorticoids and glucocorticoids. The recognition of patients with a tumor that is co-secreting aldosterone and cortisol can affect decisions to treat with glucocorticoids perioperatively to avoid adrenal crisis. CONCLUSIONS Recognition of the presence of adrenal adenomas co-secreting mineralocorticoids and glucocorticoids.Consideration for perioperative and postoperative glucocorticoid use in the treatment of co-secreting adrenal adenomas.