To analyze the incidence, characteristics and risk factors of hyperbilirubinemia after allogeneic hematopoietic cell transplantation with reduced-intensity conditioning (allo-RIC), we conducted a retrospective study in three Spanish centers. We analyzed 452 consecutive patients receiving allo-RIC. Of these, 92 patients (20%) developed marked hyperbilirubinemia (>4 mg/day or >68.4 μM) after allo-RIC. The main causes of marked hyperbilirubinemia after transplant were cholestasis due to GVHD or sepsis (n=57, 62%) and drug-induced cholestasis (n=13, 14%). A total of 22 patients with marked hyperbilirubinemia (24%) underwent liver biopsy. The most frequent histological finding was iron overload alone (n=6) or in combination with other features (n=6). In multivariate analysis, the risk factors for marked hyperbilirubinemia after allo-RIC were non-HLA-identical sibling donors (hazard ratio (HR) 2.2 (95% confidence interval (CI) 1.4-3.6) P=0.001), female donors to male recipients (HR 2.1 (95% CI 1.3-3.3) P=0.003) and high levels of bilirubin and γ-glutamyl transpeptidase before transplant (HR 4.5 (95% CI 2.5-8.4) P<0.001 and HR 4.6 (95% CI 2.6-8.1) P<0.001, respectively). Patients with marked hyperbilirubinemia showed higher 4-year nonrelapse mortality (HR 1.3 (95% CI 1-1.7), P=0.02) and lower 4-year OS (HR 1.4 (95%CI 1.3-1.7), P<0.001) than patients without. In conclusion, we confirm that marked hyperbilirubinemia is frequent and diverse after allo-RIC. Development of marked hyperbilirubinemia after allo-RIC is associated with worse outcome of the procedure.