A 60-year-old woman was admitted to our hospital with complaints of muscle weakness and erythema on her extremities. Gottron's sign, heliotrope rash, elevation of serum myogenic enzymes, electromyography and magnetic resonance imaging findings established a diagnosis of dermatomyositis (DM). She was treated with 60 mg of daily prednisolone. One week later, she suddenly developed splenic and renal infarctions, which were considered to have resulted from vasculopathy associated with DM. Cyclophosphamide and anticoagulants along with increasing the dosage of corticosteroid were effective. This is the first report describing splenic and renal infarctions in a patient with adult-onset DM.