The yellow mushy substance vomited by the cat is bile or gastric acid. At this time, the cat owner should fast the pet and observe the cat's condition closely. If the cat vomits continuously and does not get better, it may lead to gastroenteritis, pancreatitis, feline distemper infection, etc. Disease requires further confirmation by a pet doctor. If your cat only vomits yellow water, he may have eaten the wrong thing or vomited hair balls.