Orthokeratinized Odontogenic Cyst (OOC) is a rare odontogenic cyst, which is important because it has a low recurrence potential, but it has a percentage of the potential for malignant changes. OOC characteristics can be different from OKC (odontogenic keratocyst), which was once classified in its category. The microscopic view of OOC cyst is the reason for its easy identification from OKC, the orthokeratinized epithelial covering and the clear granular layer, and the hyperplasia of the basal layer, and the smooth surface of this cyst. OOC cyst treatment is conservative and can be usually carried out by enucleation. In terms of gender predominance, it is often reported in men. Furthermore, OOC is more common in the 3rd and 4th decades of life. Hereby, we report a rare case of OOC in the posterior mandible of a young adult 18-year-old boy and its treatment method. The clinical and diagnostic points of view and the treatment options were discussed in this article.