Combine mayonnaise, lemon juice, ground black pepper, sugar, salt, and seasoned salt in a bowl.
Stir the dressing ingredients very well to combine.
Now, add cooked chicken, diced red onion, finely diced celery, and chopped pecans. Stir well to combine the salad ingredients.
Finally, add diced red grapes and carefully fold in to combine.
Put the salad bowl in an airtight container and keep it in the refrigerator for 30 minutes before servings.