In a large bowl, add the salad ingredients, the shredded chicken, pasta, onion, avocado, cherry tomatoes, and basil.
In a jar, combine the ingredients for the dressing: vinegar, Italian seasoning, olive oil, salt, and pepper.
Drizzle your chicken pasta salad with the dressing. Toss gently until all the ingredients are combined. Serve the chicken pasta salad immediately, or chill for later.