The objective of this study was to describe a case of giant myelolipoma associated with undiagnosed congenital adrenal hyperplasia (CAH) due to 21-hydroxylase (21OH) deficiency. Five seven year-old male patient referred with abdominal ultrasound revealing a left adrenal mass. Biochemical investigation revealed hyperandrogenism and imaging exams characterized a large heterogeneous left adrenal mass with interweaving free fat tissue, compatible with the diagnosis of myelolipoma, and a 1.5 cm nodule in the right adrenal gland. Biochemical correlation has brought concerns about differential diagnosis with adrenocortical carcinoma, and surgical excision of the left adrenal mass was indicated. Anatomopathologic findings revealed a myelolipoma and multinodular hyperplasic adrenocortex. Further investigation resulted in the diagnosis of CAH due to 21OH deficiency. Concluded that CAH has been shown to be associated with adrenocortical tumors. Although rare, myelolipoma associated with CAH should be included in the differential diagnosis of adrenal gland masses. Moreover, CAH should always be ruled out in incidentally detected adrenal masses to avoid unnecessary surgical procedures.