Endocardial fibroelastosis (EFE) signifies the pathological process by which collagen and elastin are focally or diffuse deposited in the endocardium of the left ventricle. The new layer causes left ventricular dysfunction sometimes with fulminant progression to heart failure. EFE is a major component in many congenital heart abnormalities but can also occur in the absence of heart malformations, either as a primary process or in response to cardiac injury. The endothelial-mesenchymal transition (EndMT) abnormalities seem to be main pathogenic factor in fibroelastosis development. The "gold standard" for diagnosis of primary EFE (pEFE) is the histological examination. Additionally, genetic studies may help to establish the natural course of the disease and to communicate prophylactic measures to family members of the affected child. Moreover, in the newborn, EFE takes the form of dilated cardiomyopathy (DCM) with unfavorable evolution. The proper management should be established considering negative prognostic factors, involving early transplantation, drug therapy and long-term follow-up.