Acquired hemophilia A (AHA) is a rare coagulation disorder caused by autoantibodies against coagulation factor VIII (FVIII). We report herein a very rare case of AHA complicated by immune thrombocytopenia (ITP). A 30-year-old woman was hospitalized with severe thrombocytopenia. Her platelet count was 5,000/μl on admission, at which time APTT was normal. ITP was diagnosed and she was treated with γ-globulin, platelet transfusion, and prednisolone at 1 mg/kg/day. She was discharged after platelet count normalization and prednisolone was tapered to 5 mg/day. During the prednisolone tapering, purpura appeared on both thighs and in the left inguinal region, and APTT was found to be prolonged. She was referred to our hospital for examination of APTT prolongation. FVIII activity was markedly decreased to 7.7% and the FVIII inhibitor was positive (1.5 BU/ml), based on which AHA was diagnosed. We carefully followed this patient without intensification of immunosuppressive therapy for 7 weeks, but her platelet count decreased from 150,000/μl to 70,000/μl and the FVIII inhibitor increased to 4 BU/ml. We therefore increased prednisolone to 30 mg/day, after which her platelet count increased and complete remission of AHA was achieved by day 42. In addition, we examined the relationship of the FVIII inhibitor and FVIII binding antibody in this case.