Gather your ingredients. Shred or chop cooked chicken, dice celery, finely chop red onion, and slice grapes in half. Chop walnuts and mince parsley as needed.

In a mixing bowl, combine Greek yogurt, Dijon mustard, and lemon juice. Whisk until smooth.

Add garlic powder, salt, and black pepper. Mix well to create the dressing.

To the dressing, add the shredded chicken, celery, red onion, grapes, walnuts, and parsley. Toss gently to combine.

Taste the salad and adjust seasoning if needed.

Cover and refrigerate for at least 30 minutes to let flavors meld.

Serve chilled on greens, in a wrap, or as a sandwich.