Combine turkey, celery, onions, pecans, and cranberries in a large bowl.
In another bowl, whisk together mayonnaise, mustard, lemon juice, parsley, salt, celery seed, and pepper. Taste and adjust seasonings as needed. Pour over turkey mixture and mix well to coat.
Serve immediately, or cover tightly and store in the refrigerator until ready to serve. Enjoy within 3 days.