Gingival cyst of the adult (GCA) is a rare entity and comprises around 0.3% of all odontogenic cysts. Due to its rarity, there are a few retrospective studies on it. Therefore, the aim of this study was to present casuistic data of a 20-year retrospective study performed in a Brazilian oral pathology reference center. All cases diagnosed as gingival cyst of the adult in the last 20 years were retrieved from the files of the Oral Pathology Service. Data from the lesions and patients were tabulated and presented descriptively. From a total of 68,229 oral biopsies, 7,023 were odontogenic cysts, and among these only 20 cases were diagnosed as gingival cyst of the adult, resulting in the largest series of gingival cyst of the adult, from a single center, in the last 15 years. Most cases occurred in women, and although 53% affected the anterior mandible, 40% occurred in the anterior maxilla, which contrasts with the previous literature. Despite being a rare lesion GCA should be considered in the clinical differential diagnosis of gingival lesions presenting either in the maxilla or mandible.