Is boric acid poisonous to cats?

It is toxic to cats, meaning it can kill them. If you are using it for roach or other insect pest control, it is usually OK unless you put it in areas where the cat will walk, because then the cat will get it on their paws and lick it off. Do not use boric acid at all around kittens, as they tend to explore more and would be more likely to get into it and die from it. See the Related link below.