Congenital maxillomandibular fusion is an extremely rare condition. To date, approximately 70 cases of oral synechia have been reported, and most of these involved palate-mouth floor, palate-tongue, or interalveolar synechiae. This study reported a very unique case of synechia in which the lower lip vermilion had split into two branches and formed a cordlike structure as it attached to an anterior maxillary alveolar cleft. In particular, the synechia was accompanied by a cleft lip and a lower lip pit, accentuating the rarity of the case. In this report, we analyzed the case based on the mechanisms of synechia development and related syndromes; in addition, we discussed the importance of the examinations, diagnosis, and treatment methods. Synechiae should be resolved as soon as possible, since they can severely restrict mouth opening and lead to problem with oral function, and its relation with the syndrome should be considered.