Preheat your oven to 350°F (180°C).
While the oven warms up, bring your pumpkin pie to room temperature.
Make sure your pie is in an oven-safe container, or put it on a baking tray.
Cover your slice of pie or whole pie loosely with foil. Not too tight, or the pastry will turn soggy.
Warm it up in the oven for 5-10 minutes (for a slice, whole pies will take longer).
Once heated to your satisfaction, serve immediately.