Pretransplantation nutritional status may impact outcome after allogeneic hematopoietic cell transplantation (HCT). Various simple screening tools have been developed and used to identify patients at risk of malnutrition; however, how best to use these screening tools is unclear, and their accuracy for the prediction of adverse outcomes is unknown. To investigate how these different measures contribute to outcome prediction, we examined a large cohort of adults with acute myelogenous leukemia (AML) who underwent allogeneic HCT in first or second remission at our institution between April 2006 and May 2021. We assessed the prognostic role of the Nutrition Risk Index (NRI), which combines weight loss and serum albumin, in 970 adults with AML in first or second remission who had usual body weight information available at AML diagnosis or relapse and before HCT. A low NRI at the time of conditioning for HCT was associated with higher nonrelapse mortality (hazard ratio [HR], .97; 95% confidence interval [CI], .95 to .98; P < .001) and relapse risk (HR, .98; 95% CI, .96 to .99; P < .001) and decreased relapse-free survival (HR, .97; 95% CI, .96 to .98; P < .001) and overall survival (HR, .97; 95% CI, .96 to .98; P < .001), as was a low pre-HCT serum albumin level. After multivariable adjustment, NRI, but not weight loss alone, was associated with outcome. The predictive ability of NRI was overall relatively low and comparable to that of serum albumin, with a C-statistic not exceeding .59. Taken together, our data indicate that pre-HCT level of serum albumin, an acute-phase protein recognized to more accurately reflect the severity of the inflammatory response compared with poor nutritional status, but not weight loss, is independently associated with post-HCT outcome in patients with AML. © 2022 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.