The Adenomatoid Odontogenic Tumor (AOT) represents 3% to 7% of all odontogenic tumors and is generally considered to be an uncommon tumor which occurs mostly in association with an unerupted maxillary cuspid. Some investigators consider it as a benign neoplasm, while others categorize it as a hamartomatous malformation due to limited size and lack of recurrence in most cases. Although AOT was formerly considered to be a variant of ameloblastoma and was designated as ‘adenoameloblastoma’, its clinical and biologic behaviour indicates that it is a separate entity. This manuscript describes a rare case of huge Adenomatoid odontogenic tumor occurring in the posterior mandible of a 20 year old male patient.