Sweet Potato Casserole with Marshmallows and Pecan Streusel

Creamy sweet potatoes, buttery pecan streusel, and a blanket of golden marshmallows make this sweet potato casserole the kind of cozy holiday side everyone looks forward to.

There are plenty of delicious ways to serve sweet potatoes, but around the holidays, I love leaning into their sweeter side. This casserole starts with soft sweet potatoes mashed with butter, milk, dark brown sugar, and vanilla. That alone would make a lovely side dish, but the topping is what makes this recipe special.

Instead of choosing between crunchy pecan streusel and marshmallows, this recipe uses both. The brown sugar topping bakes into buttery little clusters around the pecans, while the marshmallows puff up and turn golden on top. Spoon into it while it’s still warm, and you get creamy sweet potato, crunchy pecans, and gooey marshmallow all in one bite.

It’s cozy, festive, and just sweet enough to feel like a little treat alongside the savory dishes on the table.

Why You’ll Love This Recipe

For me, the best part of sweet potato casserole has always been the contrast between the soft filling and everything happening on top. This recipe really delivers on that.

The sweet potato layer is creamy without losing the flavor of the potatoes themselves. Dark brown sugar and vanilla bring out their natural sweetness, while butter and whole milk make the filling rich and smooth.

Then there’s the topping! A simple brown sugar and pecan streusel adds plenty of buttery crunch, and 2 1/2 cups of mini marshmallows create that classic toasted finish.

I especially love this recipe for a holiday meal because it serves 8, fits neatly into a 13″ x 9″ baking dish, and can sit right alongside turkey, stuffing, vegetables, and all the other favorites.

Sweet Potato Casserole Ingredients

Here’s a simple breakdown of what each ingredient does in this sweet potato casserole.

For the Sweet Potato Filling

Sweet Potatoes – the heart of the casserole. Once cooked and mashed, they create the soft, creamy base and bring plenty of natural sweetness.
Eggs – help the sweet potato mixture set as it bakes, giving the filling a rich, almost custard-like texture.
Unsalted Butter – adds richness and buttery flavor while helping make the mashed sweet potatoes smooth and creamy.
Whole Milk – loosens the mashed sweet potatoes and gives the filling a softer, creamier consistency.
Dark Brown Sugar – adds sweetness along with a deeper caramel and molasses flavor that pairs beautifully with sweet potatoes.
Vanilla Extract – adds a warm, sweet aroma and rounds out the flavors in the filling.
Kosher Salt – balances the sweetness and helps all the other flavors stand out.

For the Pecan Streusel & Marshmallow Topping

Dark Brown Sugar – gives the streusel its rich sweetness and helps create those delicious caramel-like crumbles as it bakes.
All-Purpose Flour – gives the streusel structure so the brown sugar and butter form into little crumbly clusters instead of melting completely into the potatoes.
Unsalted Butter – brings the streusel together and gives the topping its rich, buttery texture.
Raw Pecans – add a nutty flavor and a welcome crunch that contrasts with the creamy sweet potato filling.
Mini Marshmallows – create the classic finishing layer. They puff up in the oven and become soft and gooey underneath with a beautifully golden, toasted top.

Step-by-Step Instructions

Potatoes

Arrange a rack in center of oven; preheat to 350°. Place potatoes in a large pot and cover with water by about 2″. Bring to a boil, then reduce heat to medium-low. Bring to a simmer and cook until there’s no resistance when potatoes are pierced with a knife or fork, 15 to 20 minutes.
Drain, return potatoes to pot, and let cool slightly.
Mash potatoes with a masher or fork. Alternatively, use a potato ricer and rice the potatoes directly into a large bowl. Add eggs, butter, milk, brown sugar, vanilla, and salt, and mix until incorporated. Transfer to a 13″ x 9″ baking dish.

Streusel Topping & Assembly

In a medium bowl, using a rubber spatula or fork, mix brown sugar, flour, and butter until clumps form. Stir in pecans, then spread over potatoes. Top with marshmallows.
Bake casserole until warmed through and marshmallows are golden brown, about 25 minutes.

Expert Tips

This casserole is simple to put together, but a few little details make a difference.

Cook the sweet potatoes until they’re truly tender. You shouldn’t have to fight them with your masher! When a fork or knife slides easily into the potatoes, they’re ready. Properly cooked potatoes will give you a much softer, creamier filling.

Let them cool a little before adding the eggs. After draining the sweet potatoes, return them to the pot and give them a few minutes to cool slightly before mixing in the remaining ingredients.

Choose your favorite texture. I like that you have some flexibility here. A fork or potato masher will give the filling a little more texture, while a potato ricer will make it finer and smoother.

Keep those streusel clumps. When you combine the brown sugar, flour, and melted butter, you’re looking for little clusters rather than a perfectly smooth mixture. They’ll create those delicious buttery pockets throughout the pecan topping.

Watch the marshmallows toward the end. Once marshmallows start browning, they can go from pale to deeply toasted fairly quickly. The casserole is ready when it’s hot throughout and that marshmallow layer is beautifully golden.

Recipe Variations

I love this casserole exactly as written, especially because you get both pecans and marshmallows in every serving. But there are a couple of easy ways to adjust the topping without changing the heart of the recipe.

If pecans aren’t your favorite, try walnuts instead. They’ll still give the casserole a lovely nutty crunch.

For a nut-free casserole, simply leave out the pecans. You’ll still have the buttery brown sugar streusel and all those toasted marshmallows on top.

You can also play with the texture of the potatoes. Mash them with a fork if you like a more rustic filling, or reach for a potato ricer when you want them especially smooth.

Storage & Reheating

If you’re lucky enough to have leftovers, cover the casserole dish or transfer the casserole to an airtight container. It will keep in the refrigerator for 3 to 5 days.

This is also a handy casserole to prepare for the freezer. If you plan to freeze it, prepare and bake the casserole without the pecan or marshmallow topping. Let it cool completely, cover it well, and freeze.

When you’re ready to serve it, thaw the casserole overnight in the refrigerator. Add the topping and bake according to the recipe.

For refrigerated leftovers, reheat them until warmed through. Keep an eye on the marshmallow topping as you go—you want it warm and soft without letting it become overly browned.

Serving Suggestions

Sweet potato casserole always feels at home on a holiday table. I especially like serving it alongside savory dishes, where its buttery sweetness can balance all those salty, herby flavors.

Pair it with roast turkey, baked ham, or roasted chicken, then round out the meal with stuffing, green beans, roasted vegetables, cranberry sauce, and warm dinner rolls.

Because this casserole is already rich and sweet, simple vegetable sides are especially nice with it. Roasted Brussels sprouts, green beans, a crisp green salad, or roasted broccoli can bring some freshness to the plate.

And definitely serve the casserole warm if you can! That’s when the filling is soft and creamy, the pecan streusel is buttery and crisp, and the toasted marshmallows are at their gooey best.

Recipe FAQs

1. Can I make sweet potato casserole ahead of time?

Yes, you can easily prep this casserole ahead of time. Make the sweet potato filling and spread it into the baking dish, then cover and refrigerate for up to 1 day. Add the pecan streusel and marshmallows right before baking so the topping stays fresh.

2. How do I keep sweet potato casserole from getting watery?

Make sure to drain the sweet potatoes really well after boiling. I also like to return them to the warm pot for a few minutes before mashing. This gives some of that extra moisture a chance to evaporate and helps keep the filling creamy instead of watery.

3. Why are there eggs in sweet potato casserole?

The eggs help the filling set while it bakes and give it that soft, rich texture. Just make sure you let the potatoes cool slightly before adding the 4 eggs. You don’t want to stir eggs into piping-hot potatoes.

4. How do I know when sweet potato casserole is done?

Bake the casserole at 350°F for about 25 minutes. You’ll know it’s ready when the filling is warmed all the way through and the marshmallows on top are puffed and golden brown. Keep an eye on them during those last few minutes since marshmallows can toast pretty quickly.

5. Can I freeze sweet potato casserole?

Yes, you can definitely freeze it. I recommend preparing and baking the casserole without the pecan or marshmallow topping. Let it cool, cover it well, and freeze. When you’re ready to serve, thaw it overnight in the refrigerator, add the toppings, and bake according to the recipe.

Sweet Potato Casserole with Marshmallows and Pecan Streusel

Creamy mashed sweet potatoes are baked beneath a layer of buttery brown sugar and pecan streusel, then finished with mini marshmallows that turn soft and golden in the oven. The combination gives you a smooth, rich filling with a crisp, nutty topping and a toasted marshmallow finish.

Print Pin

Course: Side Dish

Cuisine: American

Keyword: Sweet Potato Casserole, Sweet Potato Casserole with Marshmallows

Prep Time: 20

Cook Time: 40

Total Time: 1

Servings:

Ingredients

Sweet Potato Filling

5 large sweet potatoes, peeled, cubed (about 8 cups)
4 large eggs
1/2 cup (1 stick) unsalted butter, melted
1 cup whole milk
1/2 cup (107 g.) packed dark brown sugar
2 tsp pure vanilla extract
1 tsp kosher salt

Pecan Streusel & Topping

1 cup (213 g.) packed dark brown sugar
1/2 cup (60 g.) all-purpose flour
4 tbsp (1/2 stick) unsalted butter, melted
1 cup coarsely chopped raw pecans
2 1/2 cups mini marshmallows

Instructions

Prepare the Sweet Potatoes

Position an oven rack in the center and preheat the oven to 350°F.
Put the cubed sweet potatoes in a large pot and add enough water to cover them by approximately 2 inches. Bring the water to a boil, then lower the heat to medium-low. Maintain a gentle simmer for 15 to 20 minutes, or until a knife or fork slides easily into the potatoes without resistance.
Drain the sweet potatoes and return them to the pot. Allow them to cool for a short time.
Mash the potatoes using a potato masher or fork. Alternatively, pass them through a potato ricer into a large bowl.
Add the eggs, melted butter, whole milk, dark brown sugar, vanilla extract, and kosher salt. Mix until everything is evenly incorporated.
Transfer the sweet potato mixture to a 13" x 9" baking dish and spread it evenly.

Make the Streusel and Assemble

In a medium bowl, combine the dark brown sugar, flour, and melted butter with a rubber spatula or fork until the mixture forms clumps.
Stir the chopped pecans into the streusel.
Distribute the pecan streusel evenly over the sweet potato mixture, then cover the top with the mini marshmallows.
Bake for about 25 minutes, until the casserole is heated all the way through and the marshmallows have turned golden brown.

Notes

Nutrition

Estimated per serving based on 8 servings. The original recipe card lists 636 calories per serving; the remaining values are estimates and can vary depending on ingredient brands and the size of the sweet potatoes.

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