Arm wrestling is a popular activity enjoyed by men and women of all ages. Although uncommon, several cases of arm wrestling injuries have been reported in the medical literature. Fractures of the humerus sustained during arm wrestling are rare clinical entities that can be confused with pathologic fractures. A butterfly fragment subtype of comminuted humeral fracture is an even more exceptional presentation of arm wrestling injury. We herein present a case of comminuted oblique fracture with a large butterfly fragment of the distal humerus in a 25-year-old man who had been involved in arm wrestling. Midway during the struggle while straining to overcome his opponent, the patient heard a loud snapping noise and felt sudden intense pain in his right arm. Radiologic findings revealed a comminuted oblique fracture at the distal third of the humeral shaft with a large butterfly fragment. It is thought that fracture of the humeral shaft during arm wrestling is the result of bending moment, axial compression and torsional forces applied to the humerus. This type of fracture may occur in anyone of any age engaging in this type of sport. The author suggests awareness of this entity and recommends appropriate radiologic and neurologic examination for injuries involving intense muscular contractions. Because of the possibility of participants sustaining such an injury, arm wrestling should not be considered a totally benign injury. Arm wrestlers should be conscious of the risks of practicing this activity.