Whisk 1 box pudding mix with 1/2 of the milk in a bowl until smooth, about 2 minutes. Repeat with second box of pudding mix and remaining milk in another bowl.
Pour 1 bowl pudding into graham cracker crust. Put 1/2 of the marshmallows on the pudding. Top with remaining pudding, then layer with marshmallows. Put whipped topping over the marshmallows and level it out with a spatula.
Chill in the refrigerator before serving, 1 to 2 hours.
5-Ingredient S'mores Pie · Dinner Match Lab | Dinner Match Lab