Objective: To report long-term outcome in a mare that had extensive rostral mandibulectomy to remove an ameloblastoma. Study Design: Clinical report. Animals: A 21-year-old mare. Methods: An ameloblastoma, located in the rostral aspect of the mandible, was removed by complete en-bloc resection of the tumor, removing most of the mandibular symphysis. Results: The day after surgery, the remaining mandibular symphysis (<5mm) fractured causing marked instability of the hemi-mandibles. Partial wound dehiscence occurred 5 days after surgery; however, the mare was able to eat well and the incision healed within 2 weeks. At 18 months, there was bony fusion of the hemi-mandibles and mild protrusion of the tongue. Conclusion: Extensive rostral mandibulectomy (up to the caudal edge of the mandibular symphysis) can apparently be performed in a horse without internal or external stabilization, and yield a cosmetic and functional outcome.