As osteomas of the bones including the jaws may be the initial symptom or clinical finding in the Gardner's syndrome, this entity should always be included in the differential diagnosis. A 20-year-old boy was referred to our clinic from another medical center. Extra-oral examination of the patient revealed an obvious asymmetry and disfigurement of the left mandibular corpus, angle and ramus. A panoramic radiograph revealed two huge osteomas at the angle, ramus and two smaller osteomas at the inferior border of the mandible. At the same time, there were an impacted canine and premolar. Diffuse sclerosis of the whole mandible was also seen. Upon the suspicion of Gardner's syndrome, barium passage radiographs of the intestine were requested and multiple polyps were observed. All of these findings led us to the diagnosis of Gardner's syndrome. The oral and maxillofacial surgeon and the dentist needs to be aware of the components of this entity because manifestations in the head and neck including epidermoid cysts, osteomas, odontomas, exostoses, supernumerary and impacted teeth are common. At the same time, osteomas causing disfigurement on the face related with Gardner's syndrome with increased uptake in scintigraphic examination should be treated by surgical excision of the lesions.