Dentigerous cyst (DC) is a common odontogenic cyst developed abnormally around unerupted maxillary or mandibular teeth. It is often asymptomatic and can be found incidentally on dental radiography with delayed eruption of teeth. However, it can be large and cause symptoms related to expansion and impingement on contiguous structures. Pain and swelling may be the major complains of patients. However, DC seldom caused head and neck inflammation or infection. Here, we described a 20-year-old male, who was found of a DC arising from right maxillary third molar involved the maxillary sinus and with sinusitis. We also reviewed articles to discuss the differential diagnosis of DC from other odontogenic cysts or odontogenic tumors.