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.