Preheat the oven to 350°F. Grease a 9x13-inch baking dish.
Cook the spaghetti in a large pot of salted boiling water until 2 minutes before al dente per the package instructions. Drain well.
In a large bowl, mix together the cooked spaghetti, shredded chicken, cream of mushroom soup, chicken broth, diced onion, bell pepper, pimentos, 1 ½ cups of cheddar cheese, Velveeta, seasoned salt, cayenne, salt, and black pepper until combined.
Pour the mixture into the prepared baking dish. Top with the remaining ½ cup of cheddar cheese.
Bake uncovered for 35-40 minutes until bubbly and the cheese is melted and lightly browned on top.
Let stand for 5 minutes before serving. Enjoy!
