The length of time you can leave an adult cat alone depends on the cat, his diet and your environment. In general, vets say it’s okay to leave your cat alone for up to 24 hours at a time. As long as they have access to fresh food and water and a clean litter, they should be fine for a day. If you have to leave your cat alone for more than one night, it’s advisable to get a friend or trusted cat sitter to visit your cat at home once or twice a day. That way your kitty will be in safe hands and no unforeseen problems would go unattended such as sudden illness or injury, or a broken automatic feeder. Human contact is also reassuring that someone is still caring for them and will lower your cat's anxiety.