Preheat the oven to 350 degrees F (175 degrees C).
Place the chicken in a shallow baking dish. In a medium bowl, stir together the salsa, brown sugar and mustard; pour over the chicken. Cover the dish with aluminum foil.
Bake for 1 hour in the preheated oven, until chicken is cooked through. Remove the foil for the last 15 minutes to brown the chicken.
