In a large bowl, combine chicken, grapes, celery, onion, Greek yogurt, almonds, mustard, parsley, pepper, and salt.
Toss everything together until evenly coated. Taste and adjust yogurt, salt, or pepper if needed.
Serve immediately or chill for a bit if you like it extra cold. Enjoy on bread, in a wrap, with crackers, or over a bed of greens.
Store leftovers in an airtight container in the fridge for 3–5 days.