Dentigerous cyst is the most prevalent lesion of odontogenic origin, commonly radiographically diagnosed, between the second and fourth decades of life, with a predilection for the male sex. The treatment of choice is enucleation; however, decompression is indicated for cysts that reach large proportions. The most frequent complications are expansion and resorption of the bone cortex, facial asymmetry, root resorption of adjacent teeth, migration or delay of dental eruption and compression of the lower alveolar nerve canal. Objective: To report a clinical case of a dentigerous cyst adjacent to an impacted mandibular third molar, treated with decompression and enucleation. Case report: A 39-year-old male, attended the Stomatology service with a history of a radiographic finding in the mandible. At the radiopraghic evaluation, it was possible to observe a radiolucent unilocular cystic tumor lesion, well delimited by a radiopaque, asymptomatic, intraosseous image in the region of the mandible right angle, extending from the left first pre molar to the left third molar, with the later included in a mesioangular position. The patient underwent a previous cystic decompression process, followed up regularly for 6 months, and referred for endodontic treatment of the left first and second molars to prepare for surgical enucleation and removal of the third molar. After removal, the material was sent to anatomopathological analysis, and the results confirmed the diagnosis of dentigerous cyst. The patient is being followed up without postoperative comorbidities. Conclusion: The chosen treatment allowed the maintenance of the teeth involved in the lesion, and mainly, the minimization of the enucleation procedure by previous decompression.