Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a rare disorder characterized by severe thrombocytopenia associated with total absence or a selective decrease in bone marrow megakaryocytes. A 67-year-old male presented with a 2-month bleeding tendency. He was referred to our hospital because of severe thrombocytopenia. Bone marrow biopsy showed complete absence of megakaryocytes without dysplasia in cells of the myeloid and erythroid lineages. AATP was diagnosed. In addition, mild normocytic normochromic anemia and reticulocytosis were also observed and haptoglobin was below the detectable level. Coombs-negative autoimmune hemolytic anemia (AIHA) was diagnosed based on the high titer of RBC-bound IgG and negative direct and indirect coombs test results. He was first treated with cyclosporine 200 mg per day and subsequently with prednisolone but only slight temporary improvement was achieved. Administration of eight doses of rituximab 375 mg/m(2) per week ameliorated both thrombocytopenia and anemia. AATP should be considered in the differential diagnosis of thrombocytopenia, and immunosuppressive therapy is a potential first-line treatment. This is the first case report of AATP accompanied by AIHA successfully treated with rituximab.