Preheat the oven to 350°F (175°C).
Cook the fettuccine according to package instructions until al dente.
In a large mixing bowl, combine the cooked spaghetti, shredded chicken, broccoli, Alfredo sauce, garlic powder, onion powder, salt, and pepper.
Transfer the mixture to a greased baking dish and spread it evenly.
Sprinkle the top with shredded mozzarella and grated Parmesan cheese.
Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden.
Let the casserole cool for 5-10 minutes before serving.