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Marshmallow Brownies

Rich and decadent marshmallow brownies topped with gooey marshmallows and a chocolate frosting. This tasty treat is nothing short of delicious! 

Stacked marshmallow brownies with milk.
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Marshmallow Swirl Brownies

If you are a fan of my s’mores bars, then this dessert is for you! It’s the ultimate indulgence and is made with double chocolate and fluffy marshmallows. Once you have a bite, you will be quickly converted!

I remember having these marshmallow brownies (also known as Mississippi mud brownies) at a friends house growing up. I immediately fell in love after my first bite. I’ve thought about them ever since and couldn’t wait to make them myself. Love finding older recipes!

These brownies are so yummy and pretty much any kids (or adults) dream. They start with a fudge brownie base like these chocolate mint brownies. Top with gooey marshmallows and a chocolate buttercream frosting. Seriously amazing. They’re very rich and decadent just like my oreo brownie, so I prefer to cut them into smaller size squares for serving.

Making marshmallow brownies.

3 Delicious Layers!

Brownie layer: The base of this delicious dessert is the brownie layer. I use a box of brownie mix to keep it simple. You could always make your own homemade recipe, but I like to save time by using the box mix. You honestly can’t tell the difference!

Marshmallow layer: The brownies are then topped with a layer of mini marshmallows. They cook in the oven for just a few minutes until they’re puffed up and gooey.

Chocolate frosting layer: The last layer is the chocolate buttercream. It’s a simple chocolate frosting that’s easy to make and tastes amazing. Spread it on top of the marshmallow layer for the final touch.

Mixing chocolate buttercream frosting in glass bowl.

How to Make Marshmallow Brownies

  1. BROWNIES. Prepare the brownie mix according to package directions. Pour into a greased 9×9″ pan and bake for 30 minutes, or until almost done.
  2. MARSHMALLOWS. Remove brownies from oven, then evenly sprinkle the mini marshmallows on top. Bake for about 3 minutes, or until the marshmallows have puffed up. Remove from oven and let cool.
  3. FROSTING. Beat the frosting ingredients in a large bowl with an electric mixer until smooth and creamy. Place a few spoonfuls of the frosting on top of the marshmallow layer and spread with a spatula.
Spreading chocolate buttercream frosting over marshmallow brownies.

Baking Tips

  • I like to line my pan with parchment paper and lightly grease to prevent the marshmallows from getting stuck to the pan.
  • Use a 9×9″ pan for thicker brownies and 9×13″ pan for thinner brownies.
  • If using a 9×13″ pan, I’d recommend adding an extra cup of marshmallows and doubling the frosting.
  • Add 1/2 cup chocolate chips to the brownie batter for even more chocolate flavor.
  • Use a plastic knife to easily cut the brownies and wipe it clean after each cut. Make sure they’ve cooled for about 30 minutes before cutting.
  • Don’t overbake! The brownies should be gooey and fudgy. I use the toothpick method to check if they’re done (stick a toothpick in the center of the brownies – it should come out clean).
Cut marshmallow brownies.

More Brownie Recipes

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stacked marshmallow brownies

Marshmallow Brownie Recipe

4.95 from 17 votes
↑ Click stars to rate now!
Author: Jamielyn Nye
Rich and decadent marshmallow brownies topped with gooey marshmallows and a chocolate frosting. This tasty treat is nothing short of delicious! 
Prep Time: 15 minutes
Cook Time: 30 minutes
Total Time: 45 minutes
Servings: 20


  • 18 ounce box brownie mix , plus ingredients on box
  • 2 cups mini marshmallows , more if needed

Chocolate frosting:


Make the brownies:

  • Preheat the oven to 350ºF. For thick brownies, spray a 9×9" pan with non-stick spray or line with parchment paper. If you'd like to make thinner brownies, use a 9×13" pan.
  • Prepare the brownie mix according to the package directions. Then pour batter into the prepared pan. Bake for 30 minutes, or until almost done. Do not overcook. Remove from oven and then sprinkle marshmallows over the top so that they are covering the brownies in an even layer. Bake an additional 3 minutes, or until the marshmallows have puffed up. Remove from oven and allow to cool.

Make the frosting:

  • Combine the butter, powdered sugar, cocoa powder, milk and vanilla in a large bowl. Beat with electric beaters until smooth. Add more milk or powdered sugar if needed to reach a smooth and creamy frosting. Then place spoonfuls on top of the marshmallows once cooled. Gently spread evenly.
  • I like to cut the brownies in 5×4 rows with a plastic knife.


If you make in a 9×13″ pan, you may want to double the frosting and use an extra cup of mini marshmallows. 
Make sure to use fresh marshmallows for optimal flavor. 
If you want to make these brownies even richer, add 1/2 cup chocolate chips in the brownie batter before baking. 


Calories: 185kcal | Carbohydrates: 33g | Protein: 1g | Fat: 5g | Saturated Fat: 2g | Cholesterol: 6mg | Sodium: 99mg | Potassium: 6mg | Fiber: 1g | Sugar: 24g | Vitamin A: 71IU | Calcium: 2mg | Iron: 1mg

Nutrition provided is an estimate. It will vary based on specific ingredients used.

Course: Dessert
Cuisine: American

Did you make this recipe? Don’t forget to give it a star rating below!

Stacked marshmallow brownies.

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