Pseudo-pheochromocytoma is defined as an adrenal tumor that has the typical characteristics of pheochromocytoma likely hypertension but is histopathologically diagnosed to other types of adrenal tumors. 11-year-old, castrated male Maltese presented for a left adrenal mass with hypertension. According to clinical signs and radiological features, a temporary diagnosis was made of pheochromocytoma. The adrenalectomy was performed and the histopathological examination of the resected adrenal gland was diagnosed as cortical adenocarcinoma. This report describes the case of pseudo-pheochromocytoma in a dog and implies the salience that even if pheochromocytoma is diagnosed based on all test results, pseudo-pheochromocytoma should not be excluded.