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Peanut Butter Sheet Cake

This Peanut Butter Sheet Cake is the stuff of peanut butter lovers’ dreams! Satisfy your peanut butter and dessert cravings in one moist and tender cake topped with the most delicious peanut butter marshmallow icing.

Peanut Butter Sheet Cake with Peanut Butter Icing

Whenever I’m craving peanut butter (which is often, let’s be honest), this peanut butter sheet cake is my go-to. It checks all the boxes needed to satisfy the craving: perfectly moist, the exact right amount of peanut butter flavor, and of course a sweet and creamy peanut butter frosting.

Some peanut butter cakes or cookies can get dry or crumbly. That is NOT the case here. Along with an incredibly tender texture that melts in your mouth it’s topped with creamy marshmallow peanut butter frosting. Everyone always raves about the frosting! 

Anywhere it goes, this easy cake is a hit with peanut butter lovers, and just about everyone else. Bake it, freeze it, or enjoy it fresh for days! Snacking cakes don’t get more delicious than this.

Why You’ll Love This Peanut Butter Cake

  • Easy. You won’t need any complicated ingredients or fancy techniques to make this recipe. That’s the beauty of a sheet cake, it’s ridiculously simple!
  • Full of peanut butter flavor. Peanut butter is infused into the cake and the icing, so every bite of this dessert is bursting with rich peanut butter flavor.
  • Perfect texture. Every slice is tender, moist and fluffy. Did I mention this cake is 100% irresistible?
  • Ideal for potlucks! This cake is perfect for serving a crowd. For this reason, I love bringing it to potlucks and family gatherings!
Slices of peanut butter sheet cake with peanut butter frosting.

What You’ll Need

Here’s a quick look at what you’ll need to make this peanut butter cake. Be sure to scroll down to the recipe card for specific amounts.

  • Peanut Butter: You can use creamy peanut butter, or crunchy peanut butter for added texture! The choice is yours. You’ll need it for both the cake as well as the marshmallow peanut butter icing.
  • Buttermilk: This is the not-so-secret ingredient for cake that’s super moist and tender! Plus, the flavor adds a bit of tang. No buttermilk in the fridge? Check out my buttermilk substitute tutorial.
  • Butter: Unsalted or salted, cut into cubes, plus extra for the icing.
  • Large Eggs
  • Vanilla: Pure vanilla extract is best for flavor, but imitation will also work in a pinch.
  • Vegetable Oil: Or another neutral cooking oil, like canola.
  • Evaporated Milk: Adds extra sweetness and smoothness to the icing.
  • Mini Marshmallows: The base for the delicious marshmallow and peanut butter icing!
  • Granulated Sugar
  • Dry Ingredients: All Purpose Flour, Baking Soda, and Salt

How to Make Peanut Butter Cake

Are you ready to make the best peanut butter sheet cake? Here’s how to do it:

Peanut butter cake batter being whisked.
  • Mix the Batter: Set aside the flour and dry ingredients in one bowl, and the buttermilk and wet ingredients in another. Next, you’ll prep the peanut mixture by bringing water and butter to a boil, and stirring in the peanut butter and oil. Add the peanut mixture to the flour mixture, followed by the buttermilk mixture, whisking as you go. 
  • Bake the Cake: Pour the batter into a lined jelly-roll style pan. Bake the cake in the oven until the center is set and it passes the toothpick test (a toothpick inserted into the middle comes out clean).
  • Cool. Let the cake cool for a bit so that it doesn’t melt the icing. If you can let it cool to room temperature that’s ideal!
  • Make the Icing: Bring the evaporated milk, sugar, salt and butter to a boil while continuously stirring. Once this is taken off the heat, melt in the peanut butter and marshmallows. While the cake is still warm, pour the icing over top. Use a spatula to spread it evenly across the cake, then leave it to cool. Once the cake is cooled completely, slice and serve!

Tips for the Best Peanut Butter Cake

  • Can I Use a Smaller Pan?: If you’d prefer to make this peanut butter cake in a 9×13 inch pan, it will still be delicious! Just increase the baking time to 35-40 minutes to account for the extra thickness.
  • If the Peanut Butter Mixture Is Really Hot: Adding the peanut butter mixture to the flour first should be enough to cool it off before it’s combined with the eggs/wet ingredients. However, if you’re concerned that the mixture is still hot enough to start cooking the eggs, leave it for a few minutes to cool before going ahead with the recipe as directed.
  • Can I Use Natural Peanut Butter? I’d recommend sticking to Jiffy peanut butter for this sheet cake. Natural peanut butters have a tendency to separate, which can lead to mixed results.

Topping Ideas:

I like to think of a sheet cake as my own personal canvas for all sorts of toppings! While this peanut butter cake is delicious all on its own, there are so many topping ideas you can choose from, too:

Square slices of peanut butter sheet cake with peanut butter frosting.

How to Store:

Store peanut butter cake airtight at room temperature for up to 3 days. If you’d like to extend the shelf-life, keep it covered in the fridge for up to 4-5 days.

Can I Freeze This Cake?

To freeze this peanut butter cake (and to avoid messing up the icing), once it’s cooled completely, pop the whole pan into the freezer to pre-freeze. When the sheet cake is frozen solid, wrap it in a double layer of plastic wrap plus an extra layer of foil. The cake can stay frozen for up to 3 months!

Thaw the cake overnight in the refrigerator before carefully unwrapping it. Voila! Your pre-made cake is ready to serve.

More Peanut Butter Dessert Ideas:

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A slice of moist peanut butter sheet cake is lifted with a spatula.

Peanut Butter Sheet Cake

5 Stars 4 Stars 3 Stars 2 Stars 1 Star 5 from 3 reviews
  • Author: Shelly
  • Prep Time: 15 minutes
  • Cook Time: 25 minutes
  • Total Time: 40 minutes
  • Yield: 20 servings 1x
  • Category: Dessert
  • Method: Oven
  • Cuisine: American


The stuff of peanut butter lovers’ dreams! You’ll love serving up a slice of this dreamy Peanut Butter Sheet Cake topped with peanut butter marshmallow icing. Perfect for gatherings and potlucks!



For the Cake:

  • 2 cups all purpose flour
  • 2 cups granulated sugar
  • 1 teaspoon baking soda
  • 1/2 teaspoon kosher salt
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 1/2 cup buttermilk
  • 1 cup water
  • 3/4 cup butter, cut into cubes
  • 1/2 cup peanut butter (crunchy or creamy)
  • 1/4 cup vegetable oil

For the Icing:

  • 1/3 cup evaporated milk
  • 2/3 cup granulated sugar
  • 1/4 teaspoon kosher salt
  • 2 tablespoons butter
  • 1/3 cup peanut butter (creamy or crunchy)
  • 1/2 cup mini marshmallows
  • 1 teaspoon vanilla extract 


Make the Cake

  1. Preheat your oven to 350°F. Line a 15x10x1 (jelly roll-style) pan with parchment paper. Coat with nonstick spray and set aside.
  2. In a large bowl whisk together the flour, sugar, baking soda, and salt. Set aside. 
  3. In a small bowl whisk together the eggs, vanilla, and buttermilk. Set aside.
  4. Place water and butter in a small saucepan over medium heat. Bring to a boil and remove from the heat. Stir in the peanut butter and oil, mixing until combined. Add this into the flour mixture and whisk until smooth. Then whisk in the buttermilk mixture until evenly blended. 
  5. Pour the batter into the prepared pan and bake for 20 – 25 minutes until the center is set and a toothpick inserted comes out clean. 

Make the Icing

  1. Stir together the evaporated milk, granulated sugar, salt, and butter in a medium sauce. Bring to a boil over medium heat, and boil for 2 minutes stirring constantly. Remove from the heat and stir in the peanut butter, marshmallows, and vanilla until combined and the marshmallows are melted. 
  2. Pour the icing onto the warm cake, spreading out evenly using an offset spatula. 
  3. Allow the cake to cool completely before slicing and serving. 


Store airtight at room temperature for up to 3 days. 

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10 comments on “Peanut Butter Sheet Cake”

  1. Kristin Hamilton

    Very good recipe. Love it! Super moist cake and love the icing. Everyone loved it. This is my 2nd time making it now:)

  2. Have you ever tried spreading a thin layer of jam or preserves over the cake before frosting it for a peanut butter and jelly cake or would that be to sweet??? Love all your recipes… always follow exactly including your tips and always come out perfectly.

    1. I think it would absorb right into the cake if you were to do that. I think it would taste good, but it wouldn’t be a layer of jam. Maybe you could swirl it into the icing on top before it sets!

  3. This cake was great! And the frosting was WOW!!!! I made this in a 9 x 13, it took about 45 minutes to bake, but I thought it was too much cake vs frosting. I would definitely double the frosting recipe either way becasuse it is eat out of the pan good!!! I also scattered marshmallows over the cake and then poured the warm frosting over them and the marshmallows partially melted and were soooooo yummm. This is a super fun recipe.

  4. The cake looks good but when it comes to the frosting and using evaporate milk no thanks will make my own

    1. Wow-that was super unkind of you. Just make any adjustments you want and keep your opinions to yourself. If you want to tell others how to cook, start your own food site/blog.

  5. ColleenB.~Tx.

    WOW! This looks Fantastic. We’re big peanut butter fans at this household.
    Thank you
    Even tho I haven’t made it, you deserve a 5 star rating on this. Been looking for a great peanut butter icing recipe and this one sure does look like it fits the bill

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