Allogeneic hematopoietic stem cell transplantation (allo‐HSCT) is a potentially curative strategy for acute myeloid leukemia (AML), but the impact of HLA disparity in the era of posttransplant cyclophosphamide (PTCy) and reduced‐toxicity conditioning remains unclear. We performed an EBMT registry study including 275 adult AML patients in first complete remission undergoing first allo‐HSCT between 2012 and 2023 using a uniform platform of treosulfan‐based conditioning and PTCy. Among them, 206 received haploidentical grafts and 69 underwent 9/10 mismatched unrelated donor (MMUD) transplantation. Median follow‐up was 2.5 years. At 2 years, overall survival was 73.1% after haploidentical transplantation and 71.6% after MMUD transplantation ( p  = 0.96). Leukemia‐free survival at 1 year was 66.3% and 65.2%, respectively ( p  = 0.76). Relapse incidence (17.1% vs. 18.7%, p  = 0.84) and nonrelapse mortality (16.6% vs. 16.1%, p  = 0.86) were comparable between groups. Rates of Grade II–IV and Grade III–IV acute GVHD were similar, whereas chronic GVHD was higher after haploidentical transplantation (36.4% vs. 12.7%, p  = 0.001), without differences in extensive forms. In multivariable analyses, donor type was not associated with overall survival, leukemia‐free survival, relapse incidence, or nonrelapse mortality. Increasing age adversely affected outcomes, while Karnofsky performance status ≥ 90 and reduced‐intensity conditioning were associated with improved survival. These findings suggest that, within a treosulfan–PTCy platform, major transplant outcomes are comparable between donor types, although haploidentical transplantation was associated with a higher incidence of chronic GVHD.