Dentigerous cysts are benign odontogenic cysts that develop around the crowns of permanent teeth and are considered rare in children. This article reports a case of a 10-year-old girl with an inflammatory dentigerous cyst associated with the right mandibular premolar and deeply displacing it to the lower border of the mandible. To preserve the developing mandibular premolar and the mental nerve, marsupialization of the lesion under local anesthesia was performed. During the first month postoperatively, the impacted premolar naturally started to correct its position towards the normal path of eruption. After 13 months of follow-up, full spontaneous eruption of the impacted premolar with complete resolution of the cystic lesion, new bone formation, and closure of the root apex were observed. The use of marsupialization as a first-line approach is encouraged to treat dentigerous cysts in children, as it has been reported effective in terms of conservative management.