In a large mixing bowl, combine the entire 12 ounces of thawed Cool Whip with the 3.4-ounce box of pistachio Jell-O instant pudding mix. Stir thoroughly until smooth and creamy.
Add the entire 20-ounce can of crushed pineapple, including the juice, to the bowl. Stir well to combine.
Fold in 1½ cups of miniature marshmallows and ½ cup of chopped pecans evenly throughout the mixture.
Cover the bowl and refrigerate for at least 2 hours, or until the salad is chilled and ready to serve.
Notes
Pro tip: Mixing the pudding mix with the Cool Whip first creates an extra creamy and smooth texture—trust me, it makes all the difference! :)