Background Autoimmune hemolytic anemia (AIHA) is an uncommon complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) which has only been reported in a few cases.We here aimed to explore its mechanism.Methods We retrospectively analyzed 296 patients who underwent allo-HSCT in our center from July 2010 to July 2012.Clinical manifestations were carefully reviewed and the response to currently available treatment approaches were evaluated.The survival and risk factors of AIHA patients after allo-HSCT were further analyzed.Results Twelve patients were diagnosed with AIHA at a median time of 100 days (15-720 days) after allo-HSCT.The incidence of AIHA after allo-HSCT was 4.1％.IgG antibody were detected in ten patients and IgM antibody in two patients.The two cold antibody AIHA patients had a better response to steroid corticoid only treatment and the ten warm antibody AIHA patients responded to corticosteroid treatment and adjustment of immunosuppressant therapy.Rituximab was shown to be effective for AIHA patients who failed conventional therapy.Survival analysis showed that the combination of AIHA in allo-HSCT patients hinted at poor survival.Cytomegalovirus (CMV) infection,graft-versus-host disease (GVHD) and histocompatibility leukocyte antigen (HLA) mismatch seemed to increase the risk of developing AIHA.Conclusions Patients who develop AIHA after allo-HSCT have poor survival compared to non-AIHA patients.Possible risk factors of AIHA are CMV infection,GVHD,and HLA mismatch.Rituximab is likely to be the effective treatment choice for the refractory patients.