No, NexGard is not a dewormer. It is a monthly oral flea and ticks preventative medication for dogs. The active ingredient in NexGard is afoxolaner, which kills fleas and ticks on dogs. It does not treat or prevent internal parasites such as worms. If your dog has intestinal parasites or other types of worms, your veterinarian may prescribe a different medication specifically designed to treat those types of parasites.