Sudden deaths of children and adolescents during competitive sports are usually due to congenital heart diseases. Ventricular fibrillation, however, may also occur in individuals with no underlying cardiac disease who have sustained a low-impact chest wall blow. This phenomenon is described as commotio cordis, and the overall survival rate is poor. Successful resuscitation can be achieved by prompt cardiopulmonary resuscitation and early defibrillation. We report a teenager who sustained a chest wall blow that resulted in a cardiac arrest during a rugby competition. Cardiopulmonary resuscitation was given by bystanders. The ambulance crew arrived with an automated external defibrillator. Ventricular fibrillation was detected and responded to defibrillation. Subsequent investigations including imaging and electrophysiological studies did not reveal any cardiac or brain abnormality, and the patient recovered well neurologically. Accessible cardiopulmonary resuscitation-trained personnel and automated external defibrillators should be present at all organised sporting events.