Fill the bowl of an electric mixer with nonfat Greek yoghurt and attach the whisk attachment.
Beat the yogurt until light and fluffy, approximately 10 minutes.
Add the sugar-free orange Jello and beat until fully incorporated.
Incorporate the nonfat whipped topping, stirring gently to combine.
Add the drained mandarin oranges and pineapple. Stir the mixture to combine.
Carefully fold in the mini marshmallows.
Before serving, place the mixture in the refrigerator for at least one hour.