Preheat your oven to 350°F (175°C).

Cook the spaghetti according to package instructions, drain thoroughly, and set aside.

Combine shredded chicken, cream cheese, cream of chicken soup, and butter in a large mixing bowl and mix until smooth.

Add cooked spaghetti, seasonings, spinach, and cheese topping to the bowl; stir gently until well combined.

Transfer the mixture into a greased casserole dish and spread evenly.

Bake for 30 minutes until bubbly and golden.