Dentigerous cysts is the most common developmental odontogenic cysts in jaw. The ectopic tooth in the maxillary sinus, may cause sinus ostium obstruction and mucocele formation. Dentigerous cysts is benign but relapsable. For prevention of recurrence, removal of cyst and related tooth is treatment of choice. When maxillary sinus is involved, symptoms usually appear late. So huge cysts can obstruct sinus or invade orbit. Although the classic approach for surgery is Caldwell-Luc approach, endoscopic surgery can be more useful especially in such multilobulated cases. The authors report a case (21-year old Cambodian man with persistent bilateral nasal obstruction) of a huge dentigerous cyst complicated with facial deformity that was first misdiagnosed as fibrous dysplasia. Endoscopic cyst enucleation via inferior meatal antrostomy and endoscopic removal of an unerupted tooth was done successfully without any postoperative complications. For more than one-year follow-up, post-operative healing was satisfactory and recurrence did not occur. Regarding that dentigerous cyst is a benign disease, the minimal, conservative endoscopic surgery may be considered as the treatment of choice.