Kikuchi's disease and hemophagocytic lymphohistiocytosis (HLH) present different clinical characteristics, especially in prognosis, although both diseases have the clinical similarity in initial presentations. Kikuchi's disease usually has a self-limiting clinical course, but HLH can be fatal. Accordingly, it is important that the differential diagnoses and decision as to initial treatment be made as soon as possible, at the time of clinical presentation. In the case of Kikuchi's disease accompanied with HLH, the decision concerning initial treatment can be very difficult, because these cases have been rarely reported and the prognosis is unpredictable. We report a case of a 21-year-old female diagnosed with Kikuchi's disease accompanied with HLH. Treatment involved steroid therapy, as for treatment of HLH. Recovery was complete. Kikuchi's disease with HLH can be completely treated with more aggressive therapy than used for Kikuchi's disease alone.