Preheat the oven to 350F and grease a 9X13 baking dish.
Combine the chicken, cream of mushroom soup, cheese, rice, and poppy seeds in a medium bowl. Mix well.
Scoop the mixture into the prepared baking dish and spread out evenly.
Combine the breadcrumbs and melted butter. Sprinkle evenly over the casserole.
Cover the casserole with aluminum foil and bake until bubbly, about 20 minutes.
Turn the oven to broil and return the casserole, uncovered. Broil for 1-2 minutes, until topping is crisp. Be super careful here, you can burn your casserole very easily!
Cool 5 minutes, cut into 8 equal portions and serve.