A 27-year-old man was admitted to our hospital with the complaint of general fatigue. He had cervical and mediastinal lymphadenopathy. Laboratory examination revealed anemia, hypergammaglobulinemia, and increased levels of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). A chest radiograph showed opacities in both lung fields. Pathological findings from thoracoscopic mediastinal lymph node and lung biopsies were compatible with multicentric Castleman's disease (MCD), plasma cell type with pulmonary involvement. Chemotherapy combined with radiation therapy resulted in no improvement of his lymphadenopathy and inflammatory symptoms. Eight mg/kg humanized anti-human IL-6 receptor antibody (tocilitumab) was thus administered biweekly. Soon after initiating the tocilitumab treatment, the patient's general fatigue disappeared, and anemia, CRP, ESR, hypergammaglobulinemia and lymphadenopathy all improved remarkably. Further treatment with tocilitumab for two years resulted in maintenance of this good response without any severe adverse events, but the pulmonary findings showed no obvious improvement. Tocilitumab therapy was effective in this MCD patient, however its influence on concurrent lung disease needs to be investigated further.