Schistosomus reflexus is an unusual congenital disorder, most common in ruminants and very rare in other species including cats. For the author's knowledge, there are just two previous reports of this malformation in cats but there is no reports of a in utero ultrasonographic diagnosis. A 9 years-old domestic short hair cat was presented for a pregnant ultrasonographic control with a history of know mate 2 months ago. The echographic procedure demonstrates a single fetus with cardiac contraction present within normal rate and biparietal diameter of 2.3 cm. However, lungs were almost indistinct and thorax was reduced with heart covering 80-90% of the cavity. There was an indistinct abdominal wall with a reduced cavity and no visible organs inside. Fetal liver image was found medial to a hind limb. Spinal cord takes a longitudinal disposition in a saggital view at the level of last thoracic vertebras that indicate a reflection of it. Discrete movements of the fetus were present. These fetal malformations were highly concordant with schistosomus reflexus and were diagnosed as it. The head diameter estimated gestational age was 60.5 days and, because of the severe malformations, cesarean was carried out. The extracted fetus had liver, spleen, stomach and intestine out of the abdominal cavity. Spinal cord was reflected 110° to the right. A small thorax was evident and the hind limbs were ankylosed. To the knowledge of the authors, this is the first report of an in utero ultrasonographic diagnosis of a schistosomus reflexus in a cat.