OBJECTIVE We conducted a retrospective single-center study of 106 patients to investigate the impact of prior exposure to imatinib before allogeneic hematopoietic stem cell transplantation (allo-HSCT) on outcome of HSCT for chronic myeloid leukemia (CML) in china. METHODS Patients were divided into imatinib and non-imatinib group according to whether receiving imatinib therapy before transplantation or not. Hematopoietic engraftment, prognosis, congestive heart failure (CHF), hepatic veno-occlusive disease (HVOD), graft versus host disease (GVHD), hemorrhagic cystitis and infections were compared between the two groups in early stage of transplantation (within 100 days after transplantation). RESULTS Compared to non-imatinib group, imatinib group neither had a significantly longer engraftment time nor higher incidence of HVOD, GVHD, hemorrhagic cystitis and infections (P > 0.05). However, imatinib group tended to have a statistically higher incidence of CHF (29.6% vs 8.6%, P = 0.037) and a higher 0.5-year transplant-related mortality (TRM) (27.8% vs 5.9%, P = 0.001). The estimated 10-year relapse-free survival (RFS) and 10-year overall survival (OS) were not statistically significant between the two groups (79.6% vs 62.4% P = 0.432, 68.9% vs 55.5% P = 0.086, respectively). CONCLUSION Thus, prior exposure to imatinib before transplantation does not influence the hematopoietic engraftment and incidence of early transplant-related complications. While, imatinib therapy pre-HSCT probably increases the risk of CHF and TRM in early stage of post-HSCT, and this effect can be enhanced in older age patients. However, Imatinib therapy doesn't impact RFS and OS on a long view.