Put chicken and taco seasoning in a resealable plastic bag. Seal bag and shake to coat chicken in taco seasoning. Arrange seasoned chicken in a baking dish.
Stir sour cream and salsa together in a bowl; spoon over the chicken breasts.
Bake in preheated oven for 30 minutes.
Sprinkle Cheddar cheese over the chicken breasts and continue cooking until no longer pink in the center and the juices run clear, about 10 minutes more. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).
