Methylphenidate is a stimulant drug commonly prescribed to individuals with attention-deficit/hyperactivity disorder. The suggested underlying mechanism of acute dyskinesias is dopaminergic transmission increase. We describe a 9-year-old boy with a diagnosis of attention-deficit/hyperactivity disorder admitted to emergency clinic with primarily orofacial and extremity dyskinesia after administration of a first dose of 18 mg OROS (osmotic [controlled] release oral) methylphenidate (Concerta). OROS methylphenidate was discontinued, and the patient's symptoms resolved within 20 minutes after injection of biperiden by intravenous route (0.04 mg/kg). We wish to emphasize that acute orofacial dyskinesia and extremity dyskinesia can be observed during methylphenidate therapy and that biperiden can be successfully used in the treatment of this unpleasant condition. To the best of our knowledge, this is the first report of the use of biperiden therapy in this condition. This case report highlights the importance for physicians of awareness of dyskinesia as a potential adverse effect of methylphenidate therapy and indicates benefit of biperiden therapy.