In a large mixing bowl, combine the Greek yogurt and mayonnaise. Stir until smooth and creamy.
Add the lemon juice, dried dill, salt, and pepper to the yogurt mixture, and mix well to incorporate.
Add the shredded chicken, diced celery, halved grapes, and chopped walnuts to the bowl. Gently fold the ingredients together until everything is coated with the yogurt dressing.
Taste and adjust seasoning if needed.
Cover the bowl with plastic wrap or transfer to an airtight container and refrigerate for at least 30 minutes to allow flavors to meld.
Serve chilled, garnished with chopped fresh parsley on top.
Notes
Serve on a bed of mixed greens or in a wrap. Garnish with extra walnuts or dill for added appeal.