A 9-year-old Warmblood, high-level showjumping mare sustained an acute, closed, vertical, comminuted fracture of the left accessory carpal bone (ACB) during a fall. The fracture was repaired under standing sedation and local anaesthesia, using a 6-hole APTUS® 3.5 TFP and 5 × 3.5-mm selftapping TriLock© screws. The mare recovered from surgery without complications. Upon follow-up examination 9 months post-operatively the mare was sound in all gaits and back to full athletic activity. The ACB fracture had completely healed. The displaced dorsoproximal fracture fragment was in a stationary position and there was evidence of mild nonprogressive osteoarthritis of the antebrachiocarpal joint.