Line an 8×8-inch baking dish with a layer of graham crackers.

In a bowl, whisk together the vanilla pudding mix and milk until smooth. Stir in half of the eggnog.

Spread half of the pudding mixture over the graham crackers. Add another layer of graham crackers and top with remaining pudding.

Combine Cool Whip with remaining eggnog and cinnamon; spread over the final pudding layer.

Cover with plastic wrap and chill in the refrigerator for at least four hours or overnight.

Slice into squares, serve chilled, and enjoy!