Grease a large baking dish and preheat the oven to 350°.
Place the 4 thin sliced chicken breasts in the bottom of the prepared baking dish. Season each piece of chicken with the salt, pepper and garlic powder. Spread the pesto on top of each piece of chicken and top the pesto with slices of the fresh mozzarella.
Bake uncovered for approximately 40 minutes, or until the chicken is cooked through.