BACKGROUND Haplo-identical hematopoietic stem cell transplantation (HSCT) has provided potential donors for patients lacking available HLA-matched donors. ABO blood type compatibility has been reported to be associated with HSCT outcomes. However, few studies have investigated the role of ABO compatibility in haplo-identical HSCT of AML patients. MATERIAL AND METHODS We retrospectively analyzed 42 adult acute myeloid leukemia (AML) patients who received unmanipulated haplo-identical peripheral blood HSCT at the Chinese PLA General Hospital between Jan 2013 and Dec 2017. We analyzed the role of ABO compatibility in engraftment, transfusion requirements, cytomegalovirus (CMV) and Epstein-Barr virus (EBV) viremia, acute graft-versus-host disease (GVHD), overall survival (OS), transplantation-related mortality (TRM), relapse, chronic GVHD, and post-transplant lymphoproliferative disorder (PTLD). RESULTS There were no significant differences between the ABO-matched group and the ABO-mismatched group in terms of engraftment, transfusion requirements, CMV and EBV viremia, OS, TRM, relapse, PTLD, and chronic GVHD. Univariate analysis revealed ABO incompatibility is not an independent risk factor of engraftment, transfusion requirements, CMV and EBV viremia, OS, TRM, relapse, PTLD, and chronic GVHD. We found a significantly higher cumulative incidence of aGVHD in the matched group compared with the mismatched group (80.95% vs. 42.86%, p=0.020). In multivariate analysis, ABO mismatch was associated with decreased risk of acute GVHD within 100 days after transplant (hazard ratio 0.492, 95% confidence interval 0.2123-1.14). However, the difference was not statistically significant (p=0.099). CONCLUSIONS This study demonstrated ABO incompatibility is not an independent risk factor of outcomes for AML patients who received unmanipulated haplo-identical peripheral blood HSCT. ABO compatibility might have limited value in haplo-identical donor selection.