In a mixing bowl, combine the drained crushed pineapple, instant vanilla pudding mix, and milk. Whisk until well combined and the pudding begins to thicken.
Fold in the Cool Whip until the mixture is smooth and creamy.
Pour the pineapple mixture into the pre-made graham cracker crust, spreading it evenly.
Smooth the top with a spatula and refrigerate the pie for at least 2 hours, or until set.
Before serving, garnish the pie with maraschino cherries.
Enjoy the delightful No-Bake Pineapple Pie with Cool Whip