How long do de-wormers take to work in puppies?

In about a day you'll see the dead worms in the puppies feces. It's a pretty gross sight. But it's necessary for the pups health to be dewormed. Young pups can easily die from having too many worms. You do have to deworm them more than once. Call your vet to ask what the deworming schedule should be. Also be sure to follow your vets advice on a vaccination schedule and keep your young puppy away from dogs and places where unvaccinated dogs may be or may have been till he's fully vaccinated.