In a large mixing bowl, whisk together 1 box instant vanilla pudding mix and 2 cups cold milk for 2–3 minutes until the mixture thickens.
Stir in 8 ounces of the thawed Cool Whip until fully combined.
Cover the pudding mixture and refrigerate for 10–15 minutes.
Slice 6 ripe bananas into thin slices.
Place a layer of Nilla wafers from the 11-ounce box into the bottom of a trifle dish or baking dish.
Add a layer of banana slices over the wafers.
Spread a layer of the chilled vanilla pudding mixture evenly over the bananas.
Continue layering the Nilla wafers, banana slices, and pudding mixture until all ingredients are used, ending with a layer of pudding (reserve a few Nilla wafers for topping).
Spread the remaining 8 ounces Cool Whip evenly over the top layer.
Crush a few reserved Nilla wafers and sprinkle them over the Cool Whip topping.
Cover the dish and refrigerate for at least 4 hours before serving.
Serve chilled and enjoy!
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Notes
The leftovers of the pudding will last refrigerated, covered, for up to 3 days.