A multicenter retrospective analysis of the influence of pretransplant serum ferritin (SF) was performed in 261 adult recipients of allogeneic hematopoietic stem cell transplant (allo-HSCT), including 159 patients with acute myeloid leukemia (AML), 66 with acute lymphoid leukemia (ALL) and 36 with myelodysplastic syndrome (MDS). Patients were divided into subgroups according to the pretransplant SF level [< 1000 ng/mL (low) vs. ≥ 1000 ng/mL (high)] and disease status at transplant. A high SF level was significantly associated with high disease risk (p = 0.041), but pretransplant SF and disease risk were independent significant prognostic factors for overall survival (OS), disease-free survival (DFS) and non-relapse mortality rate (NRM) on multivariate analysis. The high-SF group showed a worse outcome than the low-SF group among both standard-risk patients (OS: 54% vs. 64%, p = 0.043; DFS: 46% vs. 57%, p = 0.031) and high-risk patients (OS: 16% vs. 35%, p = 0.001; DFS: 15% vs. 34%, p = 0.001). In conclusion, a high SF at transplant adversely influences the outcome of allo-HSCT regardless of disease risk in patients with acute leukemia and MDS.