Spray a crockpot with cooking spray or use a crockpot liner.
Add the rice, chicken broth, cream of chicken soup, sour cream, onion, garlic, and Italian seasoning mix, and half of the shredded cheese to a crockpot. Mix well to combine.
Lay the chicken breasts on top of the rice mixture and season with Montreal chicken seasoning. Cover and cook on low for 6 hours.
Remove the chicken breasts from the crockpot and shred them using two forks. Return the shredded chicken to the crockpot, add the broccoli florets. Mix well.
Top everything with the remaining cheddar, cover, and cook on low for 30-45 minutes until the broccoli becomes tender and the cheese is melted. Serve and enjoy!