01 - Place pineapple and juice into a large bowl. Stir in pistachio pudding mix and stir until juice starts to thicken.
02 - Fold in whipped topping and marshmallows until evenly distributed. Fold in pistachios.
03 - Cover and refrigerate for at least 1 hour to allow pudding mix to completely dissolve.
04 - Fluff with a spoon and garnish with additional pistachios before serving. Store leftovers in a tightly covered container in refrigerator for up to 2 days.