Barley — Food safety facts
Safe to share · Cats · full breakdown on the linked food page
Cooked plain barley is safe and a decent fibre source.
Dogs and cats carry the same rating (Safe to share), so the notes below hold for either pet.
Barley is not toxic to cats. The real limit is calories, fat and salt, so treat it as a small extra alongside the normal ration rather than a meal in itself.
There is no poisoning risk here, and the usual problem is simply eating too much at once: a heavy fat or salt load can bring on loose stools or a single vomit. Offer water, keep an eye on the pet for 24 hours, and do not induce vomiting.
Barley can stay on the rotation, but only as an extra mouthful: keep the rest of the day's food unchanged and watch the litter box and how quickly they finish the next meal.
The full verdict, portion guidance and serving notes are collected on the Barley food facts page.