Background: Copeptin, C-terminal segment of pro-arginine vasopressin, is expected to be a strong novel biomarker for prognosis in acute heart failure (AHF).Participants & Methods: The study included 45 patients with acute decompensated heart failure(ADHF) to assess the relationship of serum copeptin level on admission and 72 hours after admission with adverse cardiac events (death, re-hospitalization and arrhythmias) in patients hospitalized for (ADHF) between May 2019 and November 2019 with median follow up period 6 months.Results: In this study,15 patients died, re-admission occurred in 22 patients and arrhythmias were documented in 14 patients with atrial fibrillation (n=9) and ventricular arrhythmias (n=5). Mortality rate was higher among elder smoker patients with higher heart rate, low left ventricular systolic function, higher rates of arrhythmias, impaired kidney function and high copeptin level.Furthermore, copeptin level at day 1 with cutoff value of ˃2.54 pmol/l predicted mortality with sensitivity 86.67% and specificity 53.33% while copeptin level at day 3 with cutoff value ˃ 2.74 pmol/l predicted mortality with sensitivity 93.33% and specificity 83.33%.Finally, change in copeptin level between day 1 and day 3 was associated with increased mortality. (p˂0.001)Conclusion: Copeptin is suggested to be a strong biomarker to predict adverse clinical outcomes in patients with acute decompensated heart failure including death.