I don't have any cats, but the neighbors do, and they come over sometimes. He hasn't hurt any of them. I haven't actually seen him kill anything, either. He usually just barks and harasses it until it goes away, or in the case of the opossum, I picked it up and carried it to the woods and put it in a tree. He's young, probably less than two years old and really a big old baby. I haven't encouraged killing anything because his barking and his presence are enough to keep most things away. He's also good with the other dogs. He annoys them because he wants to play with them since he's always in the backyard when I let them out or in the mudroom while my dogs are kenneled.Wish I was closer. Also is he good with cats?