Green tomatoes along with green raw potatoes are generally considered to be fairly toxic when it comes to cats. If you currently own a cat, you will want to avoid giving it tomatoes as much as possible. By giving your cat green tomatoes, you will be putting their overall health at risk.
Cats can develop problems with violent lower gastrointestinal symptoms by eating this vegetable, so you will therefore want to keep them away from your pet altogether. The leaves as well as the stems of the tomatoes are primarily what make them toxic for cats, so you will want to avoid giving them to your cat.