The dentigerous cyst is the second most frequent odontogenic cyst after the root, being typically asymptomatic and commonly incidentally diagnosed. The objective of this case was to describe a successful treatment of a dentigerous cyst associated with an unerupted lower third molar, which extended from the condyle to the premolar region, treated by decompression followed by surgical enucleation. That said, a 19-year-old female patient, black, without underlying pathologies, came to the dental office for extraction of the third molars, and after a preoperative orthopantomographic radiography, the displacement of the dental element was noted 38 for the condylar region, unilocular cystic lesion occupying the branch and mandibular body region, root resorption of the dental elements involved in the region and rejection of the mandibular canal. After cytopathological analysis of the material collected through fine needle aspiration, the diagnosis of infected dentigerous cyst was confirmed. Afterwards, extraction and decompression were performed followed by surgical enucleation. Thus, it is concluded that the treatment performed promoted a satisfactory result, given a spontaneous bone neoformation after decompression and surgical enucleation of the lesion.