Heart failure (HF) is characterized by family history and clinical examination combined with diagnostic tools such as electrocardiogram, chest x-ray and an assessment of left ventricular function by echocardiography. An early diagnosis of heart failure is still based on symptoms of dyspnea, fatigue and signs of fluid overload. Serum N-terminal pro-B-type natriuretic peptide (NT-pro BNP) is cardiac biomarker has emerged as potential predictor of heart failure. It is used as a sensitive biomarker in diagnosis and assessment severity of heart failure. This study assed the diagnostic value of (NT-pro BNP), in Iraqi children patients with heart failure and its correlation with LVEF% especially in emergency rooms of hospitals.Ninety (90) consecutive children with HF were enrolled in this study due to dilated cardiomyopathy (DCM) and (30) healthy controls. The levels of serum (NT-pro BNP) were measured, echocardiography was performed for all patients and left ventricle ejection fraction (LVEF) was calculated. The results of present study significant high mean value (± SD) of (NT-pro BNP) were recorded in serum of children with HF when compared with control group (p = 0.0001) and significant negative correlation was noticed between (NT pro-BNP) levels and left ventricular ejection fraction (r = -0.902, p = 0.0001). NT- pro-BNP appears to play a powerful role as a diagnostic and prognostic biomarker for children with heart failure and associated directly with the severity of HF in children with heart failure due to dilated cardiomyopathy (DCM