An autopsy case of congenital endocardial fibro-elastosis in a newborn infant is described. The patient revealed acute fatal type of heart failure sixty-two days after the birth. Autopsy revealed grayish white mural thickening in the left ventricle, and this change also involved the mitral valvular structure showing irregular shortening and thickening. No evidence of other intra-cardiac malformation was present. Microscopically, the mural thickening consisted of exuberant proliferation of fibrous tissue as well as the elastic fibers. There were encountered scattered foci of small round cell infiltration in the thickened endocardium and subendocardial spaces.