For most adult dogs or cats, broken bone healing time is 8 to 12 weeks. In puppies or kittens, broken bone healing time is 6 to 9 weeks. Complicated fractures can take as much as 16 weeks.Delayed Union and Non-Union Fractures.’m frequently asked how long it takes for a broken bone to heal, especially by owners who are dreading the prospect of keeping their hyperactive dog on short leash walks.