We report a girl with Johanson-Blizzard syndrome complicated by diabetes mellitus. She presented several characteristic malformations, such as aplasia of the alae nasi, deafness, dwarfism, absence of permanent teeth and malabsorption caused by disturbance of pancreatic exocrine function. At 11 years of age, glycosuria was detected at a routine outpatient examination. Repeated oral glucose tests showed a slowly progressive decline of insulin secretion and elevated blood glucose levels. The responsive secretion of insulin to glucagon or arginine loading was also low. The blood level of HbAlc was elevated over 9%. Based on these findings, insulin therapy was started when the patient was 13 years old. Our case suggests that diabetes mellitus might be considered as one of complications of Johanson-Blizzard syndrome.