Firstly, it's important to distinguish between coughing, vomiting, and gagging. Loosely speaking, if a dog coughs, they don't bring anything up. In contrast, gagging happens when your dog widely opens their mouth and makes a retching sort of sound. Unlike vomiting, your dog will not bring anything up, and your dog might cough before or after gagging. Lastly, vomiting is the most obvious, as your dog will expel their stomach contents onto the floor. Gagging is caused by kennel cough or problems with the larynx. If your dog coughs and then gags, it's likely that a lower respiratory disease and bronchitis are to blame. When your dog gags and then coughs, dysfunction of the larynx is probably a better fit. Kennel cough, a type of respiratory infection, commonly causes harsh coughing and gagging in dogs. Similarly, pneumonia can sometimes cause gagging in dogs. Laryngeal paralysis is common in elderly Labrador Retrievers and Newfoundlands, which can cause gagging, too.