In a large bowl, combine the diced chicken and halved grapes.
Add the chopped celery and red onion to the bowl.
In a separate small bowl, mix Greek yogurt, honey, and lemon juice until smooth.
Pour the yogurt mixture over the chicken and vegetables.
Season with salt and pepper to taste.
Gently toss all ingredients together until well combined.
If using, stir in the chopped walnuts for added crunch.
Chill the salad in the refrigerator for at least 30 minutes to enhance flavors.
Serve on a bed of lettuce leaves for presentation.
Enjoy your refreshing chicken salad with grapes!