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An image of a homemade Chicken Spaghetti Casserole topped with melted cheddar cheese.
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5 from 5 votes

Chicken Spaghetti Casserole

This homemade Chicken Spaghetti Casserole is adapted from the Pioneer Woman's recipe and uses a shredded Costco rotisserie chicken to make it easy to throw together on a weeknight.  Perfectly al dente pasta combine with a made-from-scratch cream of mushroom soup sauce with chopped green pepper, pimentos, diced onion, and a generous amount of shredded cheddar cheese.  This is a family favorite!
Prep Time15 mins
Cook Time40 mins
Total Time55 mins
Course: Dinner
Cuisine: American
Servings: 10 servings
Calories: 431kcal
Author: Amy Nash



  • 4 Tablespoons butter divided
  • 8 ounces cremini mushrooms diced
  • 3 Tablespoons all-purpose flour
  • 2 cups chicken broth
  • 1 cup milk
  • ¼ teaspoon salt
  • ¼ teaspoon black pepper


  • 1 pound spaghetti broken into 2-inch pieces
  • 3 Tablespoons chicken bouillon
  • 3-4 cups cooked chicken shredded
  • 1 small yellow onion chopped
  • ½ green bell pepper chopped
  • 4 ounces pimentos, drained
  • 2 ½ cups grated cheddar cheese divided
  • 1 teaspoon seasoned salt
  • ⅛ to ¼ teaspoon cayenne pepper
  • 1 cup chicken broth


  • Preheat oven to 350 degrees F.
  • Melt 1 tablespoon of butter in a large sauce pan, then add the diced mushrooms and cook for 3-5 minutes over medium-high heat, stirring frequently, until most of the liquid released from the mushrooms cooks off.
  • Add remaining butter and let melt, then sprinkle with the flour and stir and cook for 30 seconds.
  • Whisk in the chicken broth and milk, about ½ cup at a time, until combined. Stir in salt and pepper, then simmer for 3-5 minutes until slightly thickened. Remove sauce from heat and set aside.
  • Fill a large pot with water and bring to a boil. Add the spaghetti and season the water with about 1 tablespoon of salt. I also like to add 3-4 tablespoons of chicken-flavored Better Than Bouillon to the water to flavor the spaghetti noodles while they cook. Cook according to package directions until al dente, then drain.
  • In a large bowl, combine the cooked spaghetti noodles, chicken, onion, bell pepper, pimentos, 1 ¾ cups cheese, seasoned salt, and cayenne pepper. Pour the sauce over everything and stir to combine. Transfer to a 9x13-inch baking dish.
  • Pour remaining 1 cup chicken broth over the pasta, then sprinkle with the remaining ¾ cup cheese. Bake for 35 to 40 minutes until the cheese is melted and the casserole is hot and bubbly.


I use a rotisserie chicken from Costco that I pull the meat off of and shred, but the Pioneer Woman's original recipe calls for 1 cut-up fryer chicken to be placed in a large pot of water, brought to a boil, then simmered at medium heat until cooked through, about 25 minutes. Really, any cooked chicken would work, included oven roasted chicken breasts, leftover BBQ chicken, etc.
To Freeze: Assemble the casserole, then cover tightly with foil and freeze. Thaw in the fridge overnight when ready to use, then pull out and set on the counter while the oven preheats for about 15 minutes. Bake as directed above until hot all the way through.
Adapted from "The Pioneer Woman Cooks".


Calories: 431kcal | Carbohydrates: 40g | Protein: 26g | Fat: 18g | Saturated Fat: 10g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 5g | Trans Fat: 1g | Cholesterol: 76mg | Sodium: 830mg | Potassium: 459mg | Fiber: 2g | Sugar: 4g | Vitamin A: 815IU | Vitamin C: 20mg | Calcium: 259mg | Iron: 2mg