The prognosis of patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(+)ALL) relapsing after allogeneic hematopoietic stem cell transplantation is dismal. Here we describe a patient with post-transplant relapse of Ph(+)ALL, who has remained in complete remission (CR) for 30 months after relapse. A 55-year-old woman with Ph(+)ALL received allo-HSCT from an unrelated donor during first CR. The conditioning regimen consisted of fludarabine+melphalan, and graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus and short-term methotrexate. She achieved and maintained molecular remission without developing GVHD after transplantation, but suffered a hematologic relapse on day 871. She received imatinib-combined chemotherapy, and again achieved molecular remission. Since the completion of imatinib-combined chemotherapy, she has been receiving imatinib monotherapy. Although it has been reported that chemotherapy and imatinib are effective only transiently in patients with relapsed Ph(+)ALL, our patient has remained in molecular remission for 30 months after post-transplant relapse at the time of this report. Our case suggests that by continuing imatinib after the induction of molecular remission by imatinib-combined chemotherapy, the antileukemic activity of imatinib could achieve durable remission in combination with the graft-versus-leukemia effect. However, this needs to be investigated in studies involving a large number of patients.