An 81-year-old man presenting with fever, neurological symptoms, thrombocytopenia, and hemolytic anemia was diagnosed with acquired idiopathic thrombotic thrombocytopenic purpura (TTP). His disintegrin-like and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13) activity was <1% and the ADAMTS13 inhibitor titer was 3.2 BU/ml. He received plasma exchange and steroid administration until remission was achieved. Seven months later, he suffered from paralysis of the right hand, hemolytic anemia, and thrombocytopenia. We confirmed TTP recurrence based on ADAMTS13 activity <1% and an ADAMTS13 inhibitor titer of 19.4 BU/ml. Four infusions of rituximab were administered in addition to plasma exchange and steroid pulse therapy. Platelet count recovery was observed within 5 days. No severe side effects related to rituximab occurred. Although rituximab has not been approved for TTP in Japan, we report the efficacy and safety of rituximab in an elderly patient with recurrent TTP. We suggest that rituximab therapy should be started as soon as possible for recurrent TTP in patients with high titers of ADAMTS13 inhibitor.