Sweet Potato Casserole Recipe With Streusel and Marshmallows: Buttery Streusel Crunch Over Gooey Marshmallow Heaven

This sweet potato casserole recipe transforms humble sweet potatoes into a showstopping side dish with a buttery streusel topping and gooey marshmallow crown. The secret lies in perfectly mashed sweet potatoes that stay moist while baking, topped with a crispy cinnamon-sugar streusel that contrasts beautifully with the toasted marshmallows.

I've perfected this technique over years of holiday gatherings—it's the dish that disappears first and leaves everyone asking for the recipe.

The process starts with boiling and mashing the sweet potatoes until smooth, then mixing in brown sugar and spices for just the right amount of sweetness. The streusel topping comes together in minutes with flour, butter, and cinnamon, creating a crunchy contrast that balances the soft sweet potatoes.

What makes this version special is the marshmallow layer—we add them after the streusel bakes to ensure they stay perfectly gooey while the edges toast to golden perfection.

By the time it emerges from the oven, you'll have a casserole with three distinct textures: tender sweet potatoes, crispy streusel, and billowy marshmallows.

The aroma alone will have your kitchen smelling like Thanksgiving, and the visual contrast of golden brown streusel against melted marshmallows makes it impossible to resist. This recipe serves 8-10 and is perfect for holiday dinners, potlucks, or when you want to impress with a restaurant-quality side dish.

For extra flair, sprinkle a pinch of cinnamon on the marshmallows before broiling, or add chopped pecans to the streusel for crunch. The best part? It reheats beautifully, making it perfect for meal prep. Let's get started on this crowd-pleasing classic that's become a holiday tradition in my kitchen.

Ingredients for sweet potato casserole recipe with streusel and marshmallows

Sweet potatoes, buttery streusel, and gooey marshmallows—this trio creates holiday magic in every bite.

The sweet potatoes are non-negotiable—orange-fleshed ones like Jewel or Beauregard give the best texture. Trader Joe's or Whole Foods usually have them pre-peeled for convenience, but I always peel mine myself for that restaurant-quality feel. The butter in the streusel? Use European-style if you can—it's higher in fat and creates a richer crunch. For the marshmallows, Kraft or Jet-Puffed miniatures are the gold standard, but any brand works. The secret to the perfect streusel lies in keeping the butter cold—cut it into tiny cubes so it doesn't melt too fast when mixing.

No pecans? Walnuts or almonds work perfectly—just toast them first for extra flavor. Short on brown sugar? Substitute white sugar plus an extra pinch of cinnamon. The vanilla extract can be swapped for vanilla bean paste if you're feeling fancy, but pure extract is fine too. For a lower-sugar version, reduce the granulated sugar in the sweet potato layer by half and add 1 tsp of maple syrup instead. The heavy cream is optional but worth it—it makes the streusel even more decadent. If you're making this ahead, assemble everything except the marshmallows and bake the streusel layer first—it keeps beautifully in the fridge for up to 2 days.

This casserole reheats like a dream—just cover it with foil and warm at 350°F for 20 minutes. For make-ahead prep, bake the entire thing (including marshmallows) and store it at room temperature for up to 3 days, then reheat covered with foil. The streusel topping stays crispy for about 2 hours after baking, so if you're serving it later, re-crisp under the broiler for 1-2 minutes. Leftover marshmallows? Toss them in a bag and freeze for up to 3 months—they're perfect for toast or s'mores later. This dish is a crowd-pleaser that always gets rave reviews, and honestly, it's the centerpiece of my holiday table every year.

Step-by-step instructions for sweet potato casserole with streusel and marshmallows

Transform humble sweet potatoes into a decadent dessert masterpiece with this foolproof method.

Preheat your oven to 375°F while you peel and cut the 3 lb large sweet potatoes into ½-inch thick slices. Place them in a large pot and cover with cold water by about 2 inches. Bring to a boil over medium-high heat, then reduce to medium and simmer for 15-20 minutes until fork-tender.

Drain the sweet potatoes thoroughly, then transfer them to a large mixing bowl. While still warm, mash them with a potato masher or fork until completely smooth. Stir in the 0.5 cup granulated sugar, 1 tsp vanilla extract, and 0.25 cup heavy cream until fully combined. The mixture should be silky and smooth—this is your flavor foundation. I like to taste at this stage to ensure the sweetness level is perfect before adding the streusel.

In a separate large bowl, combine the 1.5 cups all-purpose flour, 1 cup packed brown sugar, 2 tbsp ground cinnamon, and 0.5 tsp salt. Use your fingers to work the dry ingredients together until evenly distributed—this prevents lumps in your final streusel. Cut in the 1 cup cold unsalted butter using a pastry cutter or your fingers, mixing until the mixture resembles coarse crumbs with pea-sized butter pieces throughout.

Add the 0.5 cup chopped pecans (if using) and the 1 whole large egg, mixing just until combined. The streusel should hold together when pressed but still maintain a crumbly texture. If it feels too wet, add 1-2 tablespoons more flour; if too dry, add 1 teaspoon more heavy cream. This topping is what creates that irresistible crunch contrast.

Spread the sweet potato mixture evenly in a 9x13-inch baking dish, using a rubber spatula to create an even surface. Sprinkle the 2 cups miniature marshmallows evenly over the top, pressing down lightly so they nestle into the sweet potato layer. This ensures they toast beautifully rather than just melt away.

Spoon the streusel mixture evenly over the marshmallows, spreading it out to cover completely. The streusel should be about ½-inch thick—this thickness gives you that perfect balance of crunch and gooey texture. Bake for 30-35 minutes until the edges of the streusel are golden brown and the marshmallows are fully melted and bubbling.

Remove the casserole from the oven and immediately sprinkle with an additional ½ cup miniature marshmallows and 1 tablespoon extra ground cinnamon. Return to the oven for 2-3 minutes just to toast the marshmallows—this creates that beautiful caramelized top layer. Watch closely so they don't burn.

Let the casserole rest for 10 minutes before serving. This resting time allows the layers to set slightly, making it easier to slice and serve. The result should be a perfectly balanced dessert with a tender sweet potato base, gooey marshmallow layer, and buttery crunchy streusel top. Serve warm with a scoop of vanilla ice cream for the ultimate indulgence.

Make-ahead tips for this dish

Pre-Bake the Streusel

Save time by assembling the streusel topping and baking it separately before adding the marshmallows. Spread the streusel mixture in a 9x13-inch baking dish and bake at 375°F for 15-18 minutes until golden.

Let it cool slightly before adding the sweet potato layer and marshmallows. This method ensures the streusel stays crispy and ready to go when you're ready to assemble the full casserole. 💡

Assemble Ahead

Prepare the entire casserole (sweet potato layer + streusel) up to adding the marshmallows, then cover tightly with airtight containers and refrigerate for up to 2 days. When ready to bake, add the marshmallows and bake as directed.

This approach keeps the sweet potatoes moist and the streusel fresh, so you only need to worry about the marshmallow step later. ❄️

Marshmallow Prep

Measure out all your marshmallows in advance and store them in a resealable bag in the freezer. When you're ready to assemble, simply sprinkle them directly from the bag onto the streusel.

This keeps them from sticking to your hands and makes the process much cleaner. I always do this for holiday prep—it saves time and reduces mess. 🍫

Bake Without Marshmallows

For a make-ahead option that reheats beautifully, bake the casserole without marshmallows, then store it covered at room temperature for up to 3 days. When ready to serve, broil for 2-3 minutes and top with fresh marshmallows.

This method works perfectly for potlucks or when you need to transport the dish. The streusel stays crispy, and you can add the marshmallows just before serving. 🔥

Freezer-Friendly

Assemble the entire casserole (including marshmallows) and bake until the streusel is golden but the marshmallows aren't fully melted. Let it cool completely, then wrap tightly in heavy-duty foil and store in the freezer for up to 3 months.

To serve, thaw overnight in the fridge, then reheat covered with foil at 350°F for 20 minutes. The marshmallows will soften perfectly, and the streusel will stay crisp. ❄️

Reheating Perfection

For the best results, reheat the casserole covered with foil at 350°F for 15-20 minutes. If the streusel loses its crunch, broil for 1-2 minutes after reheating to restore that golden texture.

I always reheat leftovers this way—they taste just as good as fresh! For extra indulgence, add a scoop of vanilla ice cream when serving. 💛

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