Ameloblastoma is a common jaw bone tumor. The majority occurs in the mandible. It was derived from the odontogenic epithelium. Some study showed cystic ameloblastoma was transformed from dentigerous cyst. There is no previous report of ameloblastoma occurring simultaneously in both the maxilla and the mandible. We report such condition in a 12-year-old boy with multiple cystic ameloblastoma may be derived from dentigerous cyst.