Broccoli is good for dogs in small amounts. If it makes up more than 5 percent of a dog's diet, some dogs can develop gastrointestinal problems, according to Can I Give My Dog.
Can I Give My Dog explains that broccoli contains a toxic substance called isothiocyanate, which can be a gastric irritant in many animals, including dogs. This is in part due to a dog's dietary system, which breaks down food in a different way from humans. Broccoli is a good source for Vitamins A, C and K, folate, manganese and fiber, notes DogChannel.com. Dogs can eat broccoli either raw or cooked, states The Daily Puppy. Chewing on a raw broccoli floret can also help keep a dog's teeth clean, notes Can I Give My Dog.