Sweet Potato Pumpkin Casserole

This sweet potato pumpkin casserole blends creamy mashed sweet potatoes with pumpkin puree, brown sugar, sour cream, butter, cinnamon and vanilla, then bakes under a layer of chopped pecans and puffy mini marshmallows. The filling turns silky and lightly spiced, the pecans get toasty and the marshmallows melt into a golden, gooey top. It is an easy side dish for holiday dinners, potlucks or any cozy fall meal.

Why You’ll Like This Sweet Potato Pumpkin Casserole

Adding pumpkin to classic mashed sweet potatoes makes the filling smoother, brighter in color and a little less heavy. Sour cream keeps it creamy with a gentle tang that balances the sweetness, while cinnamon and vanilla give it that warm, cozy flavor everyone looks forward to in the fall. The crunchy pecans and soft toasted marshmallows on top make every scoop a mix of creamy, crunchy and gooey.

• Easy to make: mash, stir, top and bake, with no special equipment needed.
• Perfect holiday side: it fits right in next to roast turkey, ham or chicken.
• Make-ahead friendly: prepare the base a day early and bake when guests arrive.
• Crowd pleaser: kids love the marshmallows and adults love the pecans.

Ingredients for Sweet Potato Pumpkin Casserole

For the Filling

• 3 large sweet potatoes, cooked and mashed
• 1 cup pumpkin puree
• 1/2 cup brown sugar
• 1/2 cup sour cream
• 4 tbsp butter, melted
• 1 tsp cinnamon
• 1 tsp vanilla extract

For the Topping

• 1 cup chopped pecans
• 2 cups mini marshmallows

You will need a large pot, a colander, a potato masher or hand mixer, a large mixing bowl and a greased 9×13-inch or 2-quart baking dish. Serves about 8 as a side dish.

Ingredient Notes

The sweet potatoes: Choose large sweet potatoes with firm, smooth skin and bright orange flesh. If yours are small, use 4 or 5.

The pumpkin: Use canned pumpkin puree (plain, not pie filling). Pie filling is already sweetened and spiced, so it would make the casserole too sweet.

The sour cream: Full-fat sour cream gives the creamiest result. Plain Greek yogurt can stand in with a slightly tangier flavor.

The marshmallows: Mini marshmallows spread evenly and toast in the time it takes the filling to heat through. Large marshmallows take longer to melt and can burn on top before they soften.

How to Make Sweet Potato Pumpkin Casserole

Step by Step

1. Prepare the oven and dish. Preheat the oven to 375°F (190°C). Grease a 9×13-inch or 2-quart baking dish with butter or cooking spray.
2. Cook the sweet potatoes. Peel the sweet potatoes and cut them into evenly sized cubes, about 1 1/2 inches. Place them in a large pot, cover with cold water and bring to a boil. Cook for about 15 to 20 minutes, until a fork slides in easily.
3. Drain and mash. Drain the cubes well in a colander and let them steam for a minute or two so extra water evaporates. Return them to the pot and mash until mostly smooth.
4. Mix the filling. Add the pumpkin puree, brown sugar, sour cream, melted butter, cinnamon and vanilla to the mashed sweet potatoes. Stir until the mixture is creamy and evenly orange with no streaks.
5. Spread and top. Spread the filling evenly in the prepared baking dish. Sprinkle the chopped pecans over the top, then cover everything with the mini marshmallows in an even layer.
6. Bake. Bake for 20 to 25 minutes, until the casserole is hot all the way through and the marshmallows are puffed and golden brown. Keep a close eye on it during the last few minutes.
7. Rest and serve. Let the casserole rest for 5 minutes so the filling settles slightly, then scoop and serve warm.

Tips for the Best Sweet Potato Pumpkin Casserole

Watch the Marshmallows Closely

Marshmallows go from golden to burnt very quickly. Check the oven often during the last 5 minutes and pull the dish as soon as the tops look toasty.

Drain the Sweet Potatoes Well

Watery sweet potatoes make a loose, runny filling. Letting the drained cubes steam dry for a minute keeps the casserole thick and creamy.

Cut Even Cubes

Cubes of the same size cook at the same speed, so you will not end up with hard lumps mixed into soft mash.

Mash While Warm

Hot sweet potatoes mash much more smoothly than cold ones. Mix in the other filling ingredients right away while the mash is still warm.

Variations

• Pecan crumble top: mix the pecans with 2 tablespoons flour, 2 tablespoons brown sugar and 2 tablespoons melted butter before sprinkling.
• Extra spice: add 1/4 teaspoon each of nutmeg and ginger, or 1 teaspoon pumpkin pie spice.
• Maple twist: replace half the brown sugar with pure maple syrup.
• Walnut swap: use chopped walnuts instead of pecans, or leave the nuts off for a nut-free dish.
• Roasted sweet potatoes: roast whole sweet potatoes at 400°F for about 45 to 60 minutes, then scoop out the flesh for a deeper, caramelized flavor.

Storage

Refrigerator: Cover leftovers tightly and refrigerate for up to 4 days. The marshmallows will soften, but the flavor stays great.

Reheating: Reheat individual portions in the microwave for 1 to 2 minutes, or cover the dish with foil and warm in a 350°F oven for 15 to 20 minutes, until heated through.

Freezer: Freeze the filling without the toppings for up to 3 months. Thaw overnight in the refrigerator, then add the pecans and marshmallows and bake as directed.

Make-ahead: Assemble the sweet potato and pumpkin base up to a day ahead, spread it in the baking dish, cover and refrigerate. Add the pecans and marshmallows just before baking, and add about 10 minutes to the baking time since the filling starts cold.

Frequently Asked Questions

Can I use canned sweet potatoes?

Yes. Use about two 29-ounce cans of sweet potatoes, drained well and mashed. Canned sweet potatoes are often packed in syrup, so you may want to reduce the brown sugar slightly.

Can I use pumpkin pie filling instead of pumpkin puree?

It is best to use plain pumpkin puree. Pie filling already contains sugar and spices, which makes the casserole overly sweet and changes the flavor balance.

How do I keep the marshmallows from burning?

Bake on the middle rack and check often near the end. If the marshmallows brown before the filling is hot, cover the dish loosely with foil for the remaining time.

Can I make sweet potato pumpkin casserole without marshmallows?

Yes. Simply top it with the pecans alone, or use the pecan crumble variation for a crunchy, less sweet topping.