Skip to Content

Peanut Butter Marshmallow Krispie Topped Brownies

Sharing is caring!

These peanut butter marshmallow Krispie topped brownies are the perfect sweet treat. Brownies topped with melted marshmallows and peanut butter chocolate Krispie crunchy treats.

ow Krispie topped brownies stacked on a white cake plate

If you’re looking for the PERFECT brownie bar cookie dessert recipe I have you covered! 

These peanut butter marshmallow Krispie topped brownies are sweet, full of chocolate flavor, and are super simple to throw together. 

They are made super easy by using box brownies but you could easily substitute your favorite homemade brownie in place. 

The topping brings a big bite of texture and the addition of peanut butter gives it that classic chocolate peanut butter combo. 

Oh, and then I threw in some marshmallows to bring in a whole s’mores vibe. 

It’s a flavor party in your mouth. 

Plus it’s a great potluck dessert because a little goes a long way this decadent treat!

ow Krispie topped brownies overhead with ingredients, a few slices a fork with a bite on it

Can I cut this recipe in half?


You can simply bake the boxed brownies in a 9×9 pan instead of a 9×14 pan. The brownies will be thicker but you only need to cover half as much.  

Just make sure to use a boxed brownie that can be baked in a 9×9 or an 8×8 pan. Some brownie mixes are specifically made for baking in a smaller pan. My favorite is the Ghirardelli boxed brownies!

Or, sometimes you can find smaller sized brownie mixes in pouches. They are usually in the same area as the ready to mix cookies. 

If you opt to cook in a 9×9 you will just cut the topping ingredients by half. 

I know it might be a little tricky to cut the 1/3 cup of chocolate chips in half but I typically just eyeball the half. Since you’re using this chocolate to just coat the Krispie cereal you don’t need to worry about being 100% precise. 

ow Krispie topped brownies shot up close so you can see the topping

How to store these brownies?

These brownies will keep covered on the counter for 2-3 days.

However, if it’s warm in your house the chocolate topping could become soft and melty. 

If your home is warmer I would suggest covering the pan with plastic wrap or foil and keeping it in the fridge. 

The brownies may be a little hard when you first take them out but they will soften up quickly.

ow Krispie topped brownies with a piece taken out with a fork

Can I leave out the peanut butter?

Yes, but it will change the texture of the chocolate Krispie topping. 

The peanut butter not only brings flavor but it helps bring in a little fat to the chocolate so it sets up firmly without becoming too hard. 

If you cannot have peanut butter I would suggest swapping it out Nutella or any other type of nut butter. 

Can I use another nut butter?

If you read above you’ll know the answer is yes! 

You can easily substitute almond butter, cashew butter, or even hazelnut butter. 

Honestly, any nut butter you can find. I have not tried using sunflower seed butter but I think it would work fine here too. 

ow Krispie topped brownies sliced on a plate with milk in the background

Can I use a different cereal?

Yes, but much like leaving out the peanut butter, changing the cereal will change the texture of the brownies. 

If you’re looking to a healthier alternative to Rice Krispies they make several different puffed brown rice kinds of cereal. They are typically found in the natural section of the grocery store. 

Although, I’m not sure healthy and this recipe goes hand in hand. 

Also, using generic rice cereal in this recipe works out perfectly well! 

Other great options would be lightly crushed rice Chex or corn flakes. 

If you want to go extra chocolate try subbing in cocoa Krispies or Cocoa Pebbles!

ow Krispie topped brownies stacked on top of each other a wooden board

Love these peanut butter marshmallow Krispie topped brownies?

Try a few of my other delicious desserts!

ow Krispie topped brownies stacked on a white cake plate

Peanut Butter Marshmallow Krispie Topped Brownies

Yield: 9x13 pan
Prep Time: 10 minutes
Cook Time: 30 minutes
Additional Time: 2 hours
Total Time: 2 hours 40 minutes

These peanut butter marshmallow Krispie topped brownies are the perfect sweet treat. Brownies topped with melted marshmallows and peanut butter chocolate krispie crunchy treats.


  • 1 (18 ounce) brownie mix
  • 4 cups miniature marshmallows
  • 1-1/3 cups semi-sweet chocolate chips
  • 1 cup creamy peanut butter
  • 3 tablespoons butter
  • 2 cups crispy rice cereal


  1. Preheat oven to temperature directed on brownie package.
  2. Line a 9x13 pan with parchment paper.
  3. Prepare brownies according to box directions.
  4. 4 minutes before the brownies are fully cooked, pull brownies from the oven, and add marshmallows on the top.
  5. Return to oven for 4 minutes to soften marshmallows.
  6. Remove from oven and spread marshmallows over the top of brownies. Let cool completely.
  7. In a microwave-safe bowl combine chocolate chips, peanut butter, and butter.
  8. Heat on high for 30 seconds.
  9. Stir and repeat until chocolate is melted and the mixture is smooth.
  10. Add cereal and stir to combine.
  11. Drop spoonfuls of chocolate mixture over the marshmallow layer, spreading as evenly as possible.
  12. Put the brownies in the refrigerator for a few hours to chill.
  13. Lift from pan and cut into squares.


Do not cut the brownies before the topping has set up. They will not hold together properly and it will result in a sticky mess.

Nutrition Information:
Yield: 12 Serving Size: 1
Amount Per Serving: Calories: 432Total Fat: 27gSaturated Fat: 12gTrans Fat: 0gUnsaturated Fat: 13gCholesterol: 8mgSodium: 168mgCarbohydrates: 50gFiber: 4gSugar: 35gProtein: 7g

This website provides approximate nutrition information for convenience and as a courtesy only. Nutrition information can vary for a variety of reasons. For the most precise nutritional data use your preferred nutrition calculator based on the actual ingredients you used in the recipe.

Did you make this recipe?

Please leave a comment on the blog or share a photo on Instagram using the hashtag #nutmegnanny

Kathy B

Monday 6th of May 2019

You say to chill in the refrigerator for "a few hours" to chill. About how long did it take until they were set enough to cut?

Tweet birds mommy

Wednesday 23rd of August 2017

I have to make these! I don't have the rice Krispies though so I'll try it with fruity pebbles. ☺


Wednesday 7th of October 2009

Do you have to have peanut butter


Saturday 25th of July 2009

A combination of my favorite ingredients. Most important CHOCOLATE.


Thursday 9th of July 2009

Wow! These look absolutely decadent yet so easy to make. Love those kind of recipes.

Skip to Recipe