Rinse the grapes under cold water and pat them dry with a paper towel. Remove any stems and place the grapes in a large mixing bowl.
Add the chopped pecans and mini marshmallows to the bowl with the grapes.
In a separate bowl, whisk together the Greek yogurt, mayonnaise, honey, vanilla extract, and salt until smooth and well combined.
Pour the yogurt mixture over the grape mixture and gently fold everything together until the grapes and nuts are evenly coated.
Cover the bowl with plastic wrap and refrigerate for at least 1 hour to allow the flavors to meld and the salad to chill.
Serve chilled as a refreshing side dish or dessert.