Oral osseous choristoma is a rare developmental alteration, their principal localization is nearly to base of the tongue (foramen caecum). The oral mucosa localization of osseous choristoma is extremely rare. At date only 10 cases of oral mucosa osseous choristoma had been reported. In the present paper we reported a new case of oral mucosa osseous choristoma in a Klippel-Feil syndrome patient. A review of available literature was made. We presented a 28 years old female patient who showed into the right oral mucosa, a hard, mobile, and asymptomatic mass, with minimum 4 years of evolution. The histological image showed a lesion constituted by lamellar bone, osteocytes and haematopoyetic tissue. The diagnosis of osseous choristoma was made. It is discusses their possible association with Klippel-Feil syndrome. The osseous choristoma of buccal mucosa is most frequently in fifth decade of the life although is reported between 12-to-64 years old, with a female predisposition.