A 53-year-old man was diagnosed with adult T-cell leukemia-lymphoma (ATL) acute type transformed from chronic type. A bone marrow analysis showed diffuse infiltration of abnormal lymphocytes and diffuse fibrotic change. He received unrelated cord blood transplantation (CBT) following reduced-intensity conditioning with complete remission of ATL after two courses of chemotherapy and achieved neutrophil and platelet engraftment. At 99 days after CBT, a bone marrow biopsy showed apparent resolution of myelofibrosis. These results suggest the therapeutic potential of CBT for patients with chemosensitive ATL with myelofibrosis.