Congenital maxillomandibular fusion is a very rare congenital anomaly in which the maxilla (medial orbital wall or maxillary process) and mandible (mandibular process or lateral lingual swelling) adhere via bony or soft tissue. It is also called congenital maxillomandibular fusion or congenital syngnathia or congenital oral synechia, but is referred to as congenital maxillomandibular fusion in this paper. We describe a case that developed in a 2-day-old male infant with cleft lip and palate. He was born at 40 weeks, 4 days’ gestation and weighed 3046 g. The Apgar score was 8/9. His condition was diagnosed as lactation disorder, cleft lip and palate, and a funicular structure from the lower lip to palate at birth, and he was admitted to our department in Okinawa Chubu Hospital. We resected the funicular structure extending anteriorly from the left lower lip to the left incisive bone. To date, five kinds of desmoplastic attachment areas have been reported, which are the residual ridge interval, floor of mouth and hard palate, tongue and hard palate, tongue and soft palate, and lower lip and the hard palate. Cleft palate is the most commonly reported complication of congenital maxillomandibular fusion, and syndromes such as Van der Woude syndrome (cleft lip and palate, lower lip fistula), popliteal pterygium syndrome (cleft lip and palate, lower lip fistula, genital malformation, limb malformation, popliteal pterygium) have also been reported. Only two cases of congenital maxillomandibular fusion in which the palate adhered to the lower lip in association with popliteal pterygium syndrome have been reported. We recently encountered a patient with bilateral cleft lip and palate who had adhesion between the lower lip and hard palate, and report this case along with a review of the literature.