Combine the cubed chicken, halved grapes, diced celery, and toasted pecans in a large mixing bowl.
Whisk together the Greek yogurt, honey, apple cider vinegar, poppy seeds, salt, and pepper in a separate small bowl until emulsified.
Pour the yogurt dressing over the chicken and fruit mixture.
Fold the ingredients together gently until all components are thoroughly and evenly coated.
Refrigerate for a minimum of 30 minutes before serving to allow the dressing to set and flavors to integrate.