Begin by chopping or shredding the chicken into small pieces and placing it in a large bowl or glass container.
Next, cut the grapes into small pieces and chop the pecans.
In a small bowl, combine the mayo, Greek yogurt, and Dijon mustard, mixing well to create the dressing.
Add the dressing, grapes, and pecans to the chicken and stir until everything is evenly combined.
Season generously with salt and pepper and mix again.
Refrigerate for about 30 minutes before serving to allow the flavors to develop.