A 14-year-old male with familial hypophosphatemic rickets, being treated with oral phosphate and calcitriol therapy, presented to the Division of Pediatric Dentistry, Children's Hospital of Pittsburgh of the University of Pittsburgh Medical Center, Pittsburgh, Pa. A panoramic radiograph showed multifocal, multilocular lesions in the mandible leading to surgical exploration and biopsy. Histopathological evaluation of the largest lesion showed features consistent with central giant cell granuloma. Given the patient's history, hyperparathyroidism was suspected. Laboratory data showed an elevated parathyroid hormone of 152 pg/ml (normal range equals nine to 69). This confirmed the diagnosis of multiple brown tumors in the mandible associated with secondary hyperparathyroidism, which was attributed to high-dose phosphate treatment. After endocrinology consultation, calcitriol therapy was increased. Improvement of the patient's brown tumors is expected with medical therapy. The purpose of this case report was to raise awareness among pediatric dentists about the maxillofacial ramifications of secondary hyperparathyroidism.