Preheat oven to 350º. Arrange chicken breasts on rimmed baking sheet. Drizzle with olive oil and sprinkle with salt and pepper. Place into oven and roast until juices run clear when pricked with a sharp knife and an instant read thermometer registers 160º F when inserted into the thickest part of the chicken, about 35 to 40 minutes. Remove chicken from the oven and allow to cool enough to handle.
Once chicken has cooled, pull chicken off the bone, discarding the skin and the bone of the chicken. Place chicken into a medium to large bowl. Add tomatoes and pesto. Stir until well combined.
Serve warm or cold. Store in an airtight container in the refrigerator if serving later.