Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is sometimes complicated by diffuse alveolar hemorrhage (DAH), which may cause respiratory failure. Venovenous extracorporeal membrane oxygenation (VV-ECMO) without an anticoagulant because of hemorrhagic status, showed the effectiveness for severe respiratory failure by DAH with AAV. A 44-year-old woman developed DAH with bowel bleeding following the onset of AAV, with positive anti-proteinase-3 (PR3) antibodies. Although ventilator management could not support her respiratory status, VV-ECMO was performed. The patient was given immunosuppressive therapy comprising a steroid pulse, plasma exchange, and cyclophosphamide. After about 10 days of VV-ECMO and immunosuppressive therapy, VV-ECMO was withdrawn, and on day 12, ventilator support was stopped. Although a thrombus developed within the inferior vena cava (IVC), which required IVC filtration, the patient was discharged on day 51. VV-ECMO support was effective for treating DAH in this patient with new-onset AAV, which takes some time to achieve remission with immunosuppressive therapy.