A dentigerous cyst of infl ammatory origin is a variant of dentigerous cyst which is commonly noticed only in the mixed dentition which diff ers from the developmental origin. It is slow growing in nature and has the tendency to cause bone expansion, displacement of adjacent teeth, tooth mobility, mild sensitivity, and deformation of roots of developing permanent teeth. The origin of this cyst is through the spread of infl ammation from the root apex of a nonvital deciduous tooth to the follicle of a developing permanent successor. The treatment of the cyst can be done by enucleation or decompression/marsupialization methods. The larger cyst can be managed conservatively by marsupialization or decompression to avoid the damage of involved developing permanent successor and should be saved wherever possible. This is a case report of dentigerous cyst of infl ammatory origin in a 12-year-old girl.