Beckwith-Wiedemann syndrome (BWS) is a rare congenital condition characterized by complex overgrowth of different body parts. Children with Beckwith-Wiedemann syndrome, particularly those with hemihypertrophy, experience an increased risk of developing benign and malignant tumors. This case report presents an 18-month-old girl with features suggestive of Beckwith-Wiedemann syndrome who developed pubic hair, high levels of testosterone, and DHEAS with normal cortisol and progesterone levels. Computed tomography revealed a left adrenal mass. Histopathological examination of the resected mass showed an adrenocortical tumor. Her postoperative evaluation showed normal testosterone and DHEAS levels. Early diagnosis and detection of intra-abdominal neoplasms in infants with Beckwith-Wiedemann syndrome are essential to avoid serious clinical complications.