Supracondylar humerus fractures are associated with neurological complications. This report describes a child who suffered from persistent myoclonus-like movements of the elbow and wrist as a consequence of a previous displaced fracture. Symptoms were progressive. Seven years later, sensation was decreased in the ulnar nerve distribution. Palpation of the ulnar nerve exacerbated the myoclonic jerks. As symptoms progressed, electoneuromyography became abnormal. Cubital tunnel release and anterior transposition of the ulnar nerve were required to reach full recovery. Long-term outcome was excellent. In conclusion, myoclonus-like movements are a rare complication of supracondylar humerus fractures, resulting from ulnar nerve injury.