In a large bowl, mix together the drained pasta, marinara sauce, Italian seasoning, half of the mozzarella cheese, and the cooked chicken until evenly combined.
Pour the pasta mixture into the dish. Evenly sprinkle the remaining mozzarella cheese, the Parmesan cheese, and the whole grain breadcrumbs over the top.
Bake uncovered until the cheese is melted and the topping turns golden, about 25 minutes.