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.
The full verdict, portion guidance and serving notes are collected on the Barley food facts page.
Short answer
Yes, cooked plain barley is safe for kittens. It's a good source of fiber. Offer it plain, watch for any signs of stomach upset, and call your vet if anything seems off.