This case report represents a rare case of ameloblastoma, unicystic type in maxilla in a 4-year-old girl. With the patient complaining of an asymptomatic swelling of the right maxilla at presentation, the computed tomography demonstrates a well-defined 2.5 cm × 3.2 cm × 4 cm radiolucency of the right maxilla with full expansion into maxillary sinus. The lesion was treated only by marsupialization and peripheral osteotomy because of the patient's age with future planning of second surgery. The histopathological examination confirmed the diagnosis of a unicystic type of ameloblastoma