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Dystonic reactions are complication of medications that act on dopaminergic pathways. Dystonic reactions occur often as a side effect following administration of medications that block dopamine receptors like antipsychotics. But rarely, drugs that increase dopaminergic activity like methylphenidate may also cause dystonic reactions. This has been previously reported only in patients who took dopamine antagonists or, less commonly, in children with developmental abnormalities. There is also a case report about a patient, who is only under methylphenidate treatment and has dyskinesia. We report here on a child treated with methylphenidate, who experienced an acute dystonic reaction. H.S. is a 15-years-old female with ADHD. She had been received 27 mg extended-release methylphenidate for nine days. She complained for spasmodic muscular contractions of extensor side of his right hand and wrist. The parents of the child also observed the same. She was admitted to emergency service with involuntary extensor contraction, tension and severe pain. She was diagnosed as acute dystonic reaction in assessment by psychiatrist. The patient was treated with biperiden 2 mg oral tablet and intramuscular 5 mg diazepam. In psychiatric history, the patient disclosed that this adverse effect had occurred on one occasion previously when she had taken short-acting methylphenidate several years ago. She told that the muscular contractions had occurred in her feet and toes. She had no preexisting movement disorder, central nervous system injury, developmental abnormalities or any other previously reported risk factors for this side effect. In examination the patient had normal general and neurological features. Also the cranial MRI and EEG were normal. Detailed assessment showed her to be within the normal range for gross motor, fine motor, social, and language development. Family members had no movement or psychiatric disorders. Methylphenidate is a commonly used agent effective in the treatment of attention-deficit hyperactivity disorder (ADHD). There has been one case report about dyskinesia during methylphenidate treatment, so far. There are a few case reports of extrapyramidal side effects during methylphenidate treatment in patients who has been on concomitant antipsychotic medication or having neurodevelopmental abnormalities. There are also case reports of patients, who used aripiprazole and methylphenidate combined and had dyskinesia after cessation of methylphenidate. The mechanism of this side effect is unclear. We think that our case is the first dystonia that occurred during methylphenidate treatment, so we came up with the idea that, shifts in dopamine by methylphenidate might rarely cause childhood-onset movement disorders like dystonia or dyskinesias as a side affect.