Bring broth to a boil in a medium saucepan. Add chicken; cover, reduce heat, and simmer 10 minutes or until chicken is done. Remove chicken using a slotted spoon; set aside. Cool slightly, and coarsely chop.
While chicken cools, add couscous to broth; stir well. Cover and let stand 10 minutes. Place couscous in a large bowl; cool completely. Fluff with a fork. Stir in basil and next 5 ingredients (basil through garlic). Add chopped chicken, tomatoes, onions, and chickpeas; toss gently to combine. Cover and refrigerate at least 2 hours or overnight.