Preheat oven to 350 F. Lightly grease a 9x13-inch baking dish with non-stick cooking spray.
Cook the pasta as directed.
Warm the frozen spinach and drain well.
In a skillet, make the cheese sauce. Melt the butter and whisk in the flour. Then whisk in the milk and let simmer over low heat until sauce thickens. Stir in the sour cream, garlic powder 2 cheeses until they melt. Season with salt and pepper to taste. Mix in the shredded chicken and drained spinach.
In the prepared baking dish, add the cooked pasta and then pour the cheesy chicken sauce over the top and gently combine and mix well in the baking dish. Bake in the preheated oven for 15 to 20 minutes, or until warmed through.
Serve Homemade Chicken & Spinach Mac and Cheese as one dish meal, or with small side salad or veggies.