The prognosis for blastic natural killer (NK) cell lymphoma is generally dismal. We report a patient who was successfully treated with unrelated cord blood transplantation (UCBT). A 15-year-old boy was diagnosed as having blastic NK cell lymphoma in the cervical lymph nodes. Autologous peripheral blood stem cell transplantation was performed on achieving a complete remission. However, the disease recurred in the bone marrow 6 months later. Chemotherapy induced a second remission and the patient received UCBT with a conditioning regimen consisting of total body irradiation, thiotepa and cyclophosphamide. Chronic GVHD of the lung occurred, but it was well controlled with steroids. At the time of writing, he remains in remission 18 months after UCBT with an excellent performance status. UCBT may be an option for patients with blastic NK cell lymphoma.