Background: The aim of this report was to describe duodenal obstruction caused by a rubber foreign body in a cow. Case Presentation: The clinical, biochemical and ultrasonographic findings in a five-year-old Swiss Braunvieh cow with duodenal ileus caused by a calf feeding nipple are described. The main clinical signs were anorexia, ruminal tympany, decreased faecal output and abomasal reflux syndrome. Ultrasonographic examination revealed reticular hyperactivity and a dilated duodenum. A diagnosis of duodenal ileus was made and the cow underwent rightflank laparotomy, which revealed a dilation of the cranial part of the duodenum because of obstruction by a pliable foreign body. This was identified via enterotomy as a calf feeding nipple. The cow was healthy at the time of discharge four days after surgery and went on to complete a successful lactation. Conclusions: To our knowledge, this is the first description of duodenal obstruction by a calf feeding nipple. This is an interesting case, which broadens the spectrum of the causes of duodenal ileus, which is usually caused by obstruction of the duodenum by a phytobezoar.