We aimed to clarify associations between nutritional status and mortality in patients with acute renal failure. De-identified data were obtained from the Medical Information Mart for Intensive Care III database comprising more than 40,000 critical care patients treated at Beth Israel Deaconess Medical Centerbetween 2001 and 2012. Weight loss and body mass index criteria were used to define malnutrition. Data of 193 critically ill patients with acute renal failure were analyzed, including demographics, nutrition intervention, laboratory results, and disease severity. Main outcomes were in-hospital and 1-year mortality. The 1-year mortality was significantly higher in those with malnutrition than in those without malnutrition (50.0% vs 29.3%, p=0.010), but differences in in-hospital survival were not significant (p=0.255). Significant differences in mortality were found between those with malnutrition and without starting at the 52nd day after intensive care unit (ICU) discharge (p=0.036). No significant differences were found between men and women with malnutrition in in-hospital mortality (p=0.949) and 1-year mortality (p=0.051). Male patients requiring intervention with blood products/colloid supplements had greater risk of 1-year mortality, but without statistical significance. Nutritional status is a predictive factor for mortality among critically ill patients with acute renal failure, particularly 1-year mortality after ICU discharge.