A 62-year-old male who was receiving prednisolone and methotrexate for scleroderma and rheumatoid arthritis complained of diarrhea and vomiting, and was transferred to our hospital for detailed examination and treatment of renal dysfunction and thrombocytopenia. Hemolytic anemia and crushed erythrocytes were found during the patient’s course; therefore, we suspected thrombotic microangiopathy (TMA). His ADAMTS13 activity was 60.3% and his ADAMTS13 inhibitor was under 0.5. In addition, his blood culture was positive for Streptococcus pneumoniae, and we finally diagnosed Streptococcus pneumoniae-associated TMA (pTMA). The patient was treated with antibiotics and hemodialysis. The patient recovered and was discharged on the 45th hospital day. Adult pTMA cases are remarkably rare. We herein report a successfully treated adult case of pTMA.