We retrospectively studied the association between iron overload and bloodstream infections (BSI) in the 100-day period following allogeneic hematopoietic stem cell transplantation (allo-HSCT) for acute myeloid leukemia or myelodysplastic syndromes. Serum ferritin was measured before transplantation to evaluate iron overload. Of 114 adult patients who underwent transplantation between 2000 and 2008, 36 (32%) developed BSI. Of the 44 isolates, 63% were Gram-positive bacteria, 32% were Gram-negative bacteria, and 4% were fungi. The median time to the onset of the first BSI was day 28 (range day 0-95) after transplantation. Univariate analysis revealed a significantly higher incidence of BSI in the high (≥ 1,000 ng/ml, n = 57) than in the low (< 1,000 ng/ml, n = 57) ferritin group (42.1 versus 21.1%, respectively, P = 0.017). Peripheral blood stem cell transplantation (PBSCT) (n = 23) showed a greater protective effect against BSI compared with bone marrow (n = 71) and cord blood (n = 20) transplantation. Pretransplantation serum ferritin (HR = 2.844, 95% CI: 1.180-6.859, P = 0.020) and PBSCT (HR = 0.135, 95% CI: 0.025-0.717, P = 0.019) were significant factors on multivariate analysis. In conclusion, pretransplantation serum ferritin significantly predicts BSI within the 100-day period after allo-HSCT.