A rare case of a nine years old boy diagnosed as juvenile dermatomyositis (JDM) is presented. On physical examination, he had malar rash, periorbital edema and erythema. There were symmetrical proximal muscle weakness, erythema on the extensor surfaces of the legs, over the hands and knees. In laboratory examination, LDH and CPK were found to be elevated. The pattern of inflammation in muscle was detected by electromyography. A skin and muscle biopsy was carried out from the lesions. Perivascular mononuclear inflammatory cell infiltration in the upper dermis and perivascular mononuclear cell infiltration with fiber necrosis in the muscle were seen. With these clinical and laboratory findings, JDM was diagnosed and a treatment regimen with prednisolone (2 mg/kg/day) was established. On the 15th day of treatment, the symptoms and the signs began to disappear. Prednisolone was tapered and switched to low maintenance dose. In duration of 7 months follow up, the patient was healthy and no recurrence was seen.