In a large mixing bowl, whisk together the instant pistachio pudding mix and the undrained canned crushed pineapple for 2-3 minutes until thickened.

Gently fold in the thawed Cool Whip until fully combined and smooth.

Stir in the mini marshmallows and half of the chopped nuts, preserving the lightness of the mixture.

Transfer the mixture to a serving bowl, cover tightly with plastic wrap, and refrigerate for at least 1 hour.

Before serving, sprinkle the remaining chopped nuts on top and add the maraschino cherries for garnish.