In patients with chronic heart failure (CHF) admitted to the intensive care unit (ICU), blood urea nitrogen to serum albumin ratio (BAR) was identified to be an independent risk factor for in-hospital mortality and 90 day mortality.

• Using the MIMIC-III database, a total of 1,545 critically ill patients with CHF as a diagnosed comorbidity admitted to the ICU were included in this retrospective cohort study to assess the link between BAR and the prognosis of patients with CHF admitted to the ICU.

• Among participants, 90 day all-cause mortality was 27.6% (n = 427) and in-hospital mortality was 17.3% (n = 267).

• In the multiple logistic regression analysis, BAR was shown to be an independent risk factor for in-hospital mortality [relative to BAR ≤ 0.83; 0.83 < BAR ≤ 1.24: odds ratio (OR) 2.647; BAR ≥ 1.24: OR 3.628].

• In multiple COX regression analysis, an association was found between BAR and all-cause mortality at 90 day follow-up (0.83 < BAR ≤ 1.24: OR 1.948; BAR ≥ 1.24: OR 1.807; BAR ≤ 0.83 as a reference).

• Similar outcomes were indicated by the Kaplan–Meier curves.

• In predicting in-hospital mortality and 90 day all-cause mortality, areas under the receiver operating characteristic curves of 0.622 and 0.647, respectively, were yielded.