Fennel — Food safety facts
Safe to share · Dogs · full breakdown on the linked food page
The bulb and fronds are safe in small amounts.
The full verdict, portion guidance and serving notes are collected on the Fennel food facts page.
Short answer
Yes, plain boiled fennel bulb is safe for dogs in a small amount. The cooking process makes it easier to chew and digest. Just ensure it's cooled completely to avoid burning his mouth. Offer a couple of pieces and watch for any signs of an upset stomach. If he seems off, check in with your regular vet.