Background: Dilated cardiomyopathy (DCM) is considered a potential reason for heart failure in children. Serum copeptin level is utilized as a marker in different cardiovascular diseases, where copeptin level was observed to be increased with increasing severity of cardiovascular diseases. This study aims to assess the value of serum copeptin level in dilated cardiomyopathy in pediatrics. Methods: The present study was a case-control study involved 25 cases diagnosed as dilated cardiomyopathy and 25 patients diagnosed as control group. Results: The results showed presence of statistical significance decrease in weight and BMI among cases compared to control group. The study showed that two studied groups have significant difference as regard temperature, HR, RR and SBP which are higher in cases. Regarding heart failure, 60% had acute HF and 48% were stage II according to Ross classification. There was statistical significance increase in CRP and copeptin among the studied groups. Copeptin level significantly corelate with severity and outcome of dilated cardiomyopathy, so it increased in cases with acute HF and dead cases and decrease among cases that had Ross II HF. The sensitivity of copeptin at cutoff value of 11.06 in diagnosis of dilated cardiomyopathy was 100%, specificity was 100% and the accuracy was 100%. Our results show that the sensitivity of copeptin at cut off 36.13 in prediction of death was 83.3%, specificity was 88.9% and the accuracy was 88%. Conclusion: Copeptin marker has a clinical use in HF and elevation of their levels are corelated with severity of heart failure.