Abstract One month after treatment with γ-globulin for Kawasaki disease, an 18-month-old girl developed Evans' syndrome in addition to drug-induced hypersensitivity syndrome (DIHS) after a second γ-globulin treatment. She suffered from hyperbilirubinemia, hemolytic anemia, and thrombocytopenia. The findings and her clinical course involved plasma exchange and treatment with prednisolone, with good results. Peripheral lymphocyte stimulation tests indicated that γ-globulin was the likeliest cause of the DIHS. A real-time polymerase chain reaction test showed the human herpes virus (HHV)-6 genome in peripheral blood. We demonstrated that a primary infection or infection reactivation by the HHV-6 virus was involved in the development of γ-globulin-induced hypersensitivity and Evans' syndrome.