Congenital syngnathia refers to the fusion of bony tissues, a rare disorder with only 41 cases reported in the international literature from 1936 to 2009. The occurrence of syngnathia without any other associated systemic disease or congenital anomaly is extremely rare. This report presents a case of congenital syngnathia with unilateral maxillomandibular bony adhesion without any other oral or maxillofacial anomaly. No recommended protocol for surgery exists due to the rarity of the disorder. There is a very low survival rate for the few patients who have forgone surgical management. This case describes a 74-year-old female patient who was suffering from limitation of mouth opening and was subsequently diagnosed with congenital syngnathia. The surgical staff performed separation surgery and reconstructed the malformed oral vestibule and cheek using the radial forearm free flap operation.