In 3 1/2- to 4-quart slow cooker, combine chicken, corn, broth and tomatoes; mix well.
Cover; cook on low setting for 8 to 12 hours.
About 20 minutes before serving, stir rice and taco seasoning mix into soup. Increase heat setting to high; cover and cook an additional 20 minutes or until rice is tender. Stir soup before serving.