A 15-year-old Cob mare was presented for investigation of a mandibular mass. Radiography identified an oval shaped mass occupying the intramandibular space, with a heterogeneous osseous opacity throughout the left hemimandible. Histopathology combined with immunohistochemistry was consistent with a diagnosis of sclerosing odontogenic carcinoma, which to date has only been described, rarely, in human patients. The mass was removed using a mandibular-sparing surgical technique allowing preservation of the dental arcade. Follow up five years after surgery confirmed no signs of regrowth. This case report describes the successful treatment of a previously unreported mandibular neoplasm in the horse.