Conjoined twins are generated, because of rejoining parts of the inner cell mass (Embryoblast) during first week of development. Depending upon place of adhesion, it is divided into various types. Twelve cases of conjoined twins have been delivered alive in Mashhad hospitals during the last two decades. All died within two weeks of their birth. Among these twins, anatomical features of one case of thoraco-omphalopagus conjoined twins are reported here. The twins shared a common thorasic cavity with one lung on each side, one common heart surrounded by a common pericardial cavity and membranes. Congenital heart defects were included, absence of interatrial septum, persistence of interventricular foramen, unusual pulmonary and caval circulation. In two side by side abdominal cavities only one large liver was observed between two, infants which was connected to one umbilical cord. Generally, the mechanism of conjoined twins formation and presence of their malformations is not clear yet, however, they are interesting subjects for feature studies.