Dentigerous cyst (DC) is an odontogenic cyst associated with the crown of an impacted, embedded, unerupted, or developing tooth. It is the second most common type of odontogenic cysts, accounting for 14% to 24% of all jaw cysts. Although these cysts occur more frequently during the second and third decades of life, they can also be found in children and adolescents in the mixed dentition stage. Treatment of the odontogenic cyst involves enucleation or marsupialization/decompression methods. The latter approach is preferred for larger cysts, and it is especially helpful in adolescent patients in conserving the unerupted permanent successors. The aim of treatment for DC is the complete elimination of pathology and maintenance of dentition with minimal surgical intervention. Recently defined criteria for the selection of treatment modality include the cyst size and location of the cyst, patient age, dentition involved, stage of root development, position of the tooth involved in the jaw, and relationship with the surrounding vital structure. Marsupialization or decompression technique has been advocated by several authors for treating DCs among young patients. In this conservative technique, the creation of an accessory cavity helps relieve intra-cystic pressure and accelerate the healing of cystic lesion. This technique has been successfully performed and is indicated for growing children and adolescents. Here, we report a large cyst lesion in the mandible treated by marsupialization for conservative management. In conclusion, successful reduction in size was achieved, and intraoperative complication could be prevented.