Celery is safe for dogs to eat. It is low in calories and makes an ideal treat alternative for dogs. However, too much celery can cause stomach upset in dogs, so it is best to only feed it to them in small amounts a couple of times a week.
Raw celery is fine to give to dogs as long as it is washed thoroughly to remove any chemicals or dirt. The strings on celery can cause intestinal blockages in dogs and should be removed before consumption. Cutting up celery into small pieces can also make digesting it easier for dogs.