In your large mixing bowl, add the pumpkin puree, instant vanilla pudding mix, and pumpkin pie spice. Whisk everything together until it is completely smooth and there are no dry pockets of pudding mix left. This base sets the flavor foundation for the whole dip, so take an extra minute to get it fully blended.
Add the thawed whipped topping to the pumpkin mixture and use your spatula to fold it in gently. I always fold rather than stir here because stirring too hard knocks the air out and leaves you with a denser, less fluffy dip. Keep folding just until everything is evenly combined and no streaks remain.
Cover the bowl with plastic wrap or a tight-fitting lid and place it in the refrigerator for at least one hour. This chilling time lets the pudding mix set properly, which thickens the dip and helps all the flavors come together. If you have time, chilling it a bit longer only makes it better.
Once the dip has chilled and thickened, take it out and give it one gentle stir before serving. This just evens out the texture again since some settling can happen in the fridge. It only takes a few seconds and makes a noticeable difference in presentation.
Transfer the dip to your serving bowl of choice, or leave it in the mixing bowl if that works for your gathering. Set out your favorite dippers right alongside it so guests can dig in immediately. This is the moment I always look forward to, watching the bowl empty out within minutes.