Background: Malnutrition is closely associated with heart failure, and known to be closely associated with mortality and morbidity in these patients. Aims: We investigated the relationship of the prognostic nutritional index (PNI), which is a criterion of nutritional status in patients with heart failure with reduced ejection fraction (HFrEF), with prognosis and parameters indicating inflammation. Methods: 139 patients admitted to the coronary intensive care unit with symptoms of decompensated congestive heart failure were included to the study. Patients were with heart failure with ejection fraction <%40 and decompensated for any reason. Patients who died within 1 year in hospital or follow-up were considered to have reached the endpoint. Groups were divided into 2 groups as Group 1, the exitus; (23 patients, 7 M, mean age; 69.2 ± 15.0 years) and group 2, the non-exitus; (116 patients, 57 M, mean age; 69.3 ± 11.5 years). PNI was calculated with the formula ALB(g/L) + 5 × Total lymphocyte count(109/L). Results: PNI was significantly lower in group 1. Neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and systemic inflamatory index values were significantly higher in group 1. PNI was significantly associated with these parameters. Conclusion: Low PNI scores in HFrEF patients may be associated with a worse prognosis and hematological parameters indicating more negative inflammation. PNI was found to be an independent predictor of mortality.