Preheat the oven to 375˚F. Line a baking sheet with foil and lightly spray with cooking spray. Set aside.
Pat the chicken breasts with paper towels and place on the prepared baking sheet.
Sprinkle the chicken with salt and pepper. Spread the pesto over top, then sprinkle evenly with the mozzarella cheese.
Bake in the preheated oven for 25-30 minutes, then broil for an additional 1-2 minutes.