Name: Peanut Butter Swirl Brownies
Prep time: 15 min
Cook time: 25 min
Total time: 40 min
Cuisine: American
Ingredients: 1/2 cup unsalted butter, melted; 1 cup granulated sugar; 2 large eggs, room temperature; 2 teaspoons vanilla extract; 1/3 cup unsweetened cocoa powder; 1/2 cup all-purpose flour; 1/4 teaspoon fine sea salt; 1/4 teaspoon baking powder; 1/2 cup semi-sweet chocolate chips; 1/2 cup creamy peanut butter; 3 tablespoons powdered sugar; 2 tablespoons milk or heavy cream; 1/2 teaspoon vanilla extract (for the swirl); 1 pinch fine sea salt (for the swirl)

Thick, fudgy, and packed with ribbons of creamy peanut butter, these Peanut Butter Swirl Brownies are what happens when a classic chocolate brownie meets your favorite peanut butter cup. Every bite has that perfect balance of rich cocoa and salty‑sweet peanut butter, with shiny crinkly tops and gooey centers.

They’re simple enough for a weeknight bake but special enough for parties, potlucks, or school events. You only need a few pantry staples, one bowl for the brownie batter, and a small bowl for the peanut butter swirl. The result? Bakery-style brownies without the fuss.

Why You’ll Love These Peanut Butter Swirl Brownies

These brownies hit that sweet spot between indulgent and easy. Here’s why they’ll be on repeat in your kitchen:

Ultra fudgy texture. Melted butter and just the right balance of cocoa and flour create a dense, chewy brownie instead of a cakey one.
Bold peanut butter flavor. A simple peanut butter swirl mixture bakes into pockets of nutty richness in every slice.
Pretty marbled top. Dragging a knife through the peanut butter and chocolate creates a gorgeous swirl that looks impressive with minimal effort.
Pantry-friendly ingredients. Everything is simple and easy to find—no fancy chocolate bars or special equipment.
Freezer-friendly. These brownies keep well in the freezer, so you can bake once and enjoy dessert whenever the craving hits.

What Kind of Peanut Butter Works Best for Peanut Butter Swirl Brownies?

For the neatest, most defined swirls, use a smooth, shelf-stable creamy peanut butter—the kind that doesn’t separate in the jar. Brands labeled “creamy” or “smooth” with a little sugar and oil added tend to hold their shape while baking and give you bold, even streaks of peanut butter.

You can use natural peanut butter (the type you stir), but the swirl may be slightly greasier and less distinct. If you go that route, make sure it’s very well stirred, then add a bit of powdered sugar to thicken it before swirling.

Crunchy peanut butter works too if you like texture—just know your swirls will look a bit rustic with bits of peanut throughout. No matter which style you choose, stick with unsweetened or lightly sweetened peanut butter so the brownies don’t become overly sweet.

Ingredients for the Peanut Butter Swirl Brownies

Before we dive into baking, let’s walk through the ingredients and why each one matters. We won’t talk quantities here—that will all be in the recipe card—but understanding their roles helps you tweak and perfect these brownies to your taste.

Unsalted butter – Adds richness and that classic fudgy brownie texture. Using melted butter also brings out the cocoa flavor.
Granulated sugar – Sweetens the brownies and helps create a shiny, crackly top.
Large eggs – Bind the batter and contribute to that chewy, fudgy center.
Vanilla extract – Rounds out the chocolate and peanut butter flavors with a warm, cozy aroma.
Unsweetened cocoa powder – Provides deep chocolate flavor. Use natural or Dutch-processed cocoa; either works in this recipe.
All-purpose flour – Gives the brownies structure without making them dry or cakey when used in the right amount.
Fine sea salt – Balances the sweetness and makes the chocolate and peanut butter taste richer.
Baking powder – Adds just a tiny bit of lift so the brownies aren’t overly dense.
Semi-sweet chocolate chips – Melt into little chocolate pockets, boosting the chocolate factor in every bite.
Creamy peanut butter – The star of the swirl, bringing nutty flavor and buttery richness.
Powdered sugar – Sweetens and thickens the peanut butter so it swirls cleanly and bakes up soft.
Milk or cream – Loosens the peanut butter just enough to be spoonable and easy to swirl.
Extra vanilla and a pinch of salt for the swirl – Brighten and balance the peanut butter layer.

How To Make the Peanut Butter Swirl Brownies

Step 1: Prep your pan and oven

Line an 8- or 9-inch square baking pan with parchment paper, leaving an overhang on two sides to act as a sling. Lightly grease the parchment and any exposed pan edges. Preheat your oven to 350°F (175°C) so it’s hot and ready when your batter is mixed.

Step 2: Melt the butter

In a medium, microwave-safe bowl, melt the unsalted butter in short bursts until just liquefied. Let it cool for a few minutes so it’s warm but not piping hot—this helps prevent scrambling the eggs and keeps the batter glossy.

Step 3: Make the brownie batter

Whisk the granulated sugar into the melted butter until the mixture looks thick and glossy. Add the eggs and vanilla extract, whisking until the mixture is smooth and slightly lighter in color.

Sift or sprinkle in the cocoa powder, flour, baking powder, and salt. Switch to a spatula and gently fold until no dry streaks remain. Stir in the chocolate chips just until evenly distributed. The batter will be thick and fudgy.

Step 4: Mix the peanut butter swirl

In a separate small bowl, stir together the creamy peanut butter, powdered sugar, milk or cream, vanilla, and a tiny pinch of salt. The mixture should be smooth and pourable but still thick enough to sit on top of the brownie batter in dollops. Add a splash more milk if it’s too stiff or a spoonful more powdered sugar if it’s too runny.

Step 5: Layer and swirl

Spread the brownie batter evenly in your prepared pan, smoothing the top with a spatula. Drop spoonfuls of the peanut butter mixture all over the surface. Using a butter knife or skewer, gently drag through the batter in figure-eight motions to marble the peanut butter into the chocolate. Avoid over-swirling so you keep distinct ribbons of peanut butter.

Step 6: Bake to fudgy perfection

Bake the brownies for 20–25 minutes, depending on your pan size and oven. The edges should look set and slightly pulled away from the pan, and a toothpick inserted into the center should come out with a few moist crumbs (but not wet batter). Remember: slightly underbaked is better than overbaked for fudgy brownies.

Step 7: Cool, slice, and enjoy

Place the pan on a wire rack and let the brownies cool completely in the pan. This helps them finish setting and makes slicing easier. Use the parchment sling to lift the cooled slab out of the pan, then cut into squares or rectangles with a sharp knife, wiping the blade between cuts for clean edges.

Serving Peanut Butter Swirl Brownies

These brownies are rich and satisfying, so a little goes a long way. Cut them into 16 smaller squares for bite-sized treats, or into 9 larger squares if you want bakery-style portions. As written, the recipe comfortably serves about 9–16 people, depending on how generously you slice.

Serve them at room temperature for maximum fudginess, or warm slightly in the microwave for 10–15 seconds if you’d like the chocolate chips a bit melty. They’re incredible on their own, but you can dress them up with:

A scoop of vanilla or chocolate ice cream
A drizzle of warm chocolate or caramel sauce
A sprinkle of flaky sea salt

They’re perfect for dessert nights, bake sales, or a sweet finish after a cozy family dinner.

Storing Peanut Butter Swirl Brownies

Brownies store beautifully, and these peanut butter swirl ones are no exception.

At room temperature: Once completely cool, place the brownies in an airtight container with parchment between layers. Store at room temperature for up to 3 days. This keeps them soft and fudgy.
In the fridge: For a slightly firmer, chewier texture, refrigerate the container for up to 5–6 days. Let the brownies sit at room temperature for 10–15 minutes before serving if you prefer them softer.
Freezer-friendly: Wrap individual brownies tightly in plastic wrap, then place them in a freezer-safe bag or container. Freeze for up to 3 months. Thaw at room temperature or warm briefly in the microwave before enjoying.

To keep the swirl pattern looking pretty, avoid stacking warm brownies directly on top of each other, and always use parchment or wax paper between layers.

Frequently Asked Questions

Can I use a boxed brownie mix instead of making the batter from scratch?
Yes! If you’re short on time, you can absolutely start with your favorite boxed brownie mix. Prepare the mix according to the package directions, pour it into the pan, and then follow the same peanut butter swirl steps. Bake according to the box instructions, checking a few minutes early since pan sizes and ovens vary.

Can I make these brownies without eggs?
You can experiment with an egg substitute such as a flax “egg” (1 tablespoon ground flaxseed mixed with 3 tablespoons water per egg, left to thicken). The texture will be slightly less fudgy and a bit more tender, but the flavors will still be delicious. Be sure not to overbake egg-free brownies, as they can dry out faster.

What if I only have natural peanut butter?
Natural peanut butter works, but you’ll want to stir it very thoroughly so the oil is fully incorporated. Then, add a little extra powdered sugar to thicken the swirl mixture if it seems too loose. This helps it hold its shape and keeps too much oil from rising to the top during baking.

How do I know when the brownies are done?
Start checking around the 20-minute mark. The edges should look set and slightly pulled away from the pan, and the center should no longer jiggle. A toothpick inserted near the center should come out with a few moist crumbs clinging to it. If it comes out completely wet, give the pan a few more minutes.

Can I add nuts or other mix-ins?
Definitely. Chopped peanuts, walnuts, or pecans are all lovely additions. Fold about 1/2 cup of chopped nuts or chocolate chunks into the brownie batter along with the chocolate chips. Just avoid overloading the batter with too many mix-ins, which can make it harder to bake evenly.

Want More Dessert Ideas?

If these Peanut Butter Swirl Brownies disappear quickly (they will!), you might love trying some of these other treats from the blog:

Red Velvet Cheesecake Brownies – For another rich, swirled brownie moment, try these beautiful red velvet bars with a tangy cheesecake ripple. Perfect for holidays and special occasions. (https://lifewithmira.com/red-velvet-cheesecake-brownies/)
Pumpkin Coffee Cake with Cinnamon Streusel Crumble – A cozy, spiced cake with a crunchy topping that’s perfect with your morning coffee or as an afternoon snack. (https://lifewithmira.com/pumpkin-coffee-cake-with-cinnamon-streusel-crumble/)
Soft Pumpkin Snickerdoodles with Cinnamon Sugar – Soft, chewy cookies coated in warm cinnamon sugar for the ultimate fall-inspired treat. (https://lifewithmira.com/soft-pumpkin-snickerdoodles-with-cinnamon-sugar/)
Moist Pumpkin White Chocolate Chip Muffins – Tender, bakery-style muffins loaded with pumpkin and sweet white chocolate chips. Great for breakfast or dessert. (https://lifewithmira.com/moist-pumpkin-white-chocolate-chip-muffins/)
Raspberry Pie Recipe – A classic, fruity dessert with a flaky crust and juicy berry filling that pairs beautifully with a scoop of ice cream. (https://lifewithmira.com/raspberry-pie-recipe/)

Save This Pin For Later

📌 Save these Peanut Butter Swirl Brownies to your dessert or baking Pinterest board so you can come back to them any time you’re craving something rich, chocolatey, and full of peanut butter.

When you make them, let me know how they turn out. Did you go extra heavy on the peanut butter swirl? Did you add chopped nuts or extra chocolate chips on top?

I love hearing how you make these recipes your own. Questions are always welcome—share your tweaks, tips, and baking wins so we can all bake smarter together. For even more sweet treats and everyday food inspiration, you can follow along on Pinterest at Life With Mira (https://www.pinterest.com/cookminglerecipes/).

Peanut Butter Swirl Brownies