OBJECTIVE: To investigate the association between mortality and nutritional status, assessed using the Haemoglobin, Albumin, Lymphocyte, and Platelet (HALP) score and the Prognostic Nutritional Index (PNI), in patients with heart failure (HF). STUDY DESIGN: A descriptive analytical study. Place and Duration of the Study: Department of Cardiology, Gaziantep City Hospital, Gaziantep, Turkiye, from October 2023 to December 2024. METHODOLOGY: A total of 111 patients admitted to the coronary care unit due to decompensated HF were evaluated. Data on demographic characteristics, cardiac rhythm, ejection fraction, duration of hospitalisation, survival outcomes, haematological profiles, and biochemical parameters were recorded. HALP and PNI scores were subsequently calculated. The Mann-Whitney U test was used for intergroup comparisons, and the Pearson chi-square test and Fisher's exact test were used to compare categorical variables. The cut-off levels of the HALP and PNI scores were established, and their relationship with mortality was investigated. A ROC curve analysis was used to evaluate the predictive value of different indices for mortality. RESULTS: HALP (AUC = 0.700, 95% CI: 0.560-0.839; p = 0.020) and PNI (AUC = 0.770, 95% CI: 0.645-0.896; p = 0.002) demonstrated significant discriminative ability for mortality. The optimal cut-off values were ≤18.09 (sensitivity: 61.5%, specificity: 62.2%) for HALP and ≤41.30 (sensitivity: 61.5%, specificity: 61.2%) for PNI. HALP and PNI values had significant predictive value for mortality. CONCLUSION: The HALP and PNI scores, which reflect nutritional status, were associated with mortality and may provide supportive prognostic information in ICU patients with decompensated HF; however, they were not independent predictors in multivariate analysis. KEY WORDS: Heart failure, HALP, Prognostic Nutritional Index, Intensive Care Unit, Mortality.