Wash all the grapes thoroughly and pat them dry.
Halve the red and green grapes and place them in a large mixing bowl.
Add mini marshmallows to the bowl with the grapes.
Chop the pecans or walnuts and add them to the mixture.
In a separate bowl, combine Greek yogurt, honey, and vanilla extract.
Mix the yogurt mixture until well combined and creamy.
Pour the yogurt dressing over the grape mixture.
Toss everything gently until the grapes are well coated with the dressing.
Transfer the salad to a serving dish and garnish with fresh mint leaves.
Chill in the refrigerator for about 30 minutes before serving for best flavor.