Hypoalbuminaemia has been previously described to predict worse non-relapse mortality (NRM) and inferior overall survival (OS) in allogeneic haematopoietic cell transplant (allo-HCT) recipients. Here, we evaluate the role of hypoalbuminaemia (<35 g/l) at time of onset of acute graft-versus-host disease (aGVHD) when incorporated into the refined aGVHD score. The study population consisted of 522 patients, median age 53 (18-75) years, who underwent an allo-HCT mostly for haematological malignancies. Standard risk (SR) aGVHD comprised 467 patients (89%) and the number of high risk (HR) cases was 55 (11%). Median follow-up for all surviving patients was 26 (3-55) months. Two-year OS was significantly better in patients with SR aGVHD with a serum albumin ≥35 g/l compared to SR with albumin <35 g/l [70% (95% CI = 64-76%) vs. 49% (95% CI = 42-56%), P < 0·0001]. Also, patients with SR aGVHD and a serum albumin level of ≥35 g/l had a significantly lower NRM at 1-year post-transplantation [6% (95% CI = 3-10%) vs. 25% (95% CI = 20-32%), P < 0·0001]. After our findings are validated in a large cohort of patients, we propose that hypoalbuminaemia should be incorporated into the refined aGVHD risk score to further its ability to predict outcomes within this group.