Endocardial fibroelastosis (EFE) is an idiopathic disorder of the tropical and subtropical regions of the world that is characterized by the development of restrictive cardiomyopathy. It is characterized by proliferation of both elastic and collageneous fibers within the endocardium, causing diffuse or localized thickening. A three month old baby was admitted to a local hospital in Galle, with a history of sudden onset shortness of breathing for one day. Baby was found to be in a state of heart failure and died within few hours after admission. At the post-mortem examination, heart was found to be enlarged with dilated left ventricle. The endocardium of both ventricles was markedly thickened. Histopathology showed a thick layer of collagenous fibrous tissue and elastin fibres confirmed by Vangisen Elastin stain. The cause of death was given as endocardial fibroelastosis. The underlying mechanisms of myocardial fibrosis remain unclear. It is hypothesized that infectious, inflammatory and nutritional processes are involved in this process. This case highlighted the importance of special histology staining methods when arriving at the cause of death.