My cat and dog are both vomiting yellow liquid. Should I worry?

This is not specific to any disease, but indicates that something is either directly upsetting their stomachs, or generally making them feel nauseous. The yellow color is due to bile staining which doesn't tell much other than they are vomiting on an empty stomach.

One possibility is that they ate something they were not supposed to like medication, a chemical (i.e. antifreeze), raw meat, or a plant (i.e. lilies). Vomiting is often the first signs of an exposure to a toxin, so I recommend checking if it's possible for them to have eaten anything other than their normal diet.

Vomiting and nausea can also be due to an infectious disease, organ failure, or imbalance in the blood. In order to narrow down the possibilities, you would have to take them to the vet for an evaluation.

This doesn't appear to be an emergency, but if they are acting very depressed and is vomiting continuously, then it would be best to take them to the vet sooner rather than later. If they are otherwise acting normal, then it's important to not give any food for the next eight hours, but make sure they have plenty of clean water available. If they are not vomiting in eight hours, then only feed a small amount of food (about 1Tbsp.). If they keep that down, then you can feed a little more in two hours. If the vomiting is continuing tomorrow, then it's best to take them to the vet for an evaluation.

For more information about vomiting, I recommend you read the article at the link below.

https://www.petcoach.co/article/diarrhea-vomiting-in-dogs-when-to-call-your-veterinarian/

If you have further questions or need further clarification, then you may consider having an online consult with one of our vets on Petcoach. This way, you can send unlimited pictures and have a text conversation with a vet.

I hope that helps and they get better soon.