We report the case of a 69-year-old Japanese woman who presented with thrombotic thrombocytopenic purpura (TTP) which had manifested soon after the onset of adult-onset Still's disease (AOSD). Her disease was multi-drug resistant. She had undergone treatment with high-dose glucocorticoids, two courses of steroid pulse therapy, and cyclosporine A. The patient initially had a favorable response to the administration of etanercept (an anti-tumor necrosis factor agent) and glucocorticoids. However, her disease became refractory to etanercept after 6 months. Therefore, we administered tocilizumab (a humanized monoclonal anti-IL-6 receptor antibody) which dramatically improved the patient's refractory AOSD with TTP. This is the first report of an effective treatment for AOSD with TTP using the biological agents. Our report strongly suggests that biological agents, especially a humanized monoclonal anti-IL-6 receptor antibody, may be a new option for a safe and effective treatment of multi-drug-resistant AOSD and TTP associated with AOSD.