Preheat oven to 350°F.
Mix flour, pecans, and melted butter.
Press mixture into baking dish firmly.
Bake crust for 15 minutes.
Cool crust completely before adding layers.
Beat cream cheese until fluffy.
Add powdered sugar gradually.
Fold in whipped topping gently.
Spread mixture over cooled crust.
Whisk pudding mix with cold milk.
Beat for 2 minutes until thick.
Pour pudding over cream cheese layer.
Spread final whipped topping layer.
Sprinkle chopped pistachios on top.
Refrigerate for 4 hours minimum.