Preheat oven to 350°F (175°C). Lightly grease a casserole dish.
In a large bowl, combine shredded chicken, sour cream, cream of chicken soup, cheddar cheese, garlic powder, salt, and black pepper. Mix until creamy and well combined.
Spread the chicken mixture evenly into the prepared casserole dish.
Crush Ritz crackers into coarse crumbs. Mix with melted butter until coated.
Sprinkle the cracker topping evenly over the casserole filling.
Bake uncovered for 30 to 35 minutes until bubbly around the edges and golden brown on top.
Let rest for 5 minutes before serving.