Preheat oven to 350°F. Spray a 9×9-inch baking pan with nonstick cooking spray and set aside.

Cook 8 oz spaghetti in boiling water until al dente according to package directions. Drain well and set aside.

Make sure you have 1 cup cooked, shredded chicken ready.

In a large saucepan over medium heat, add 8 oz cubed Velveeta, 4 oz cubed cream cheese, the entire 14.5 oz can of Rotel tomatoes (do not drain), 10.5 oz cream of chicken soup, 1 tablespoon minced garlic, and 1 tablespoon Italian seasoning.

Stir frequently over medium heat until the cheeses melt and the sauce is smooth and uniform, about 4–6 minutes.

Remove the saucepan from heat. Stir in the cooked shredded chicken and the drained spaghetti, mixing gently until the noodles and chicken are evenly coated.

Pour the spaghetti mixture into the prepared 9×9 baking pan and spread evenly. Sprinkle 1 cup shredded mozzarella cheese over the top.

Bake uncovered in the preheated 350°F oven for 20–25 minutes, or until heated through in the center and the mozzarella is melted and bubbly.

Let the casserole rest about 5 minutes before serving.