By: Jill Mills Updated: Aug 6, 2025

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This Chocolate Zucchini Cake is rich, moist, and topped with an irresistible chocolate buttercream! It’s a must-bake every summer and a great way to use any extra zucchini.

A spatula serving a slice of chocolate zucchini cake

It’s not often that I use the oven during the summer months but when I do, it’s usually to make this chocolate zucchini cake! This recipe is right up there with zucchini bread as one of my favorite things to make when there’s an abundance of zucchini. It’s wonderful on its own but adding the chocolate buttercream really turns it into a chocolate-lover’s dream!

Why I Make This Chocolate Zucchini Cake Every Summer

Great way to use zucchini. Every August, there comes a point where there’s more zucchini than anyone knows what to do with. And as much as I love savory recipes like stuffed zucchini boats and parmesan zucchini, sweet treats like this chocolate zucchini cake are my favorite way to make sure no fresh zucchini goes to waste!
Super moist texture. Zucchini adds moisture to baked goods, which is one of the reasons I love baking with it. That, along with the oil, melted butter, and buttermilk, ensure that this chocolate zucchini cake is ultra moist.
Rich chocolate flavor. This cake tastes like a rich chocolate cake – no one will no there’s zucchini in it if you don’t tell them! Not to mention the chocolate buttercream frosting on top. Yum!

Overhead view of ingredients for chocolate zucchini cake

Recipe Ingredients

Here’s an overview of the ingredients needed to make both the cake and the frosting! Almost everything included is a pantry staple. Scroll down to the recipe card below for the exact measurements.

For the Cake

All-purpose flour
Cocoa powder – Be sure to use unsweetened cocoa powder, as sweetened will add way too much sweetness to the cake.
Baking soda – Helps the cake rise in the oven.
Salt – Balances the sweet flavors.
Brown sugar – Brown sugar adds moisture and richness to the cake, in addition to acting as the sweetener.
Vegetable oil & butter – Using a combination of vegetable oil and melted butter is my secret to getting this zucchini cake to be perfectly moist and rich.
Buttermilk – If you don’t have buttermilk, mix 1/2 cup of regular milk with 1/2 tablespoon of lemon juice or white vinegar and let it sit for 5 minutes as a substitute.
Eggs
Vanilla extract
Shredded zucchini – Lightly squeeze the zucchini once it’s grated to remove excess water.
Chocolate chips – Semi-sweet or dark chocolate are great options.

For the Chocolate Buttercream Frosting

Unsalted butter – It’s important to use unsalted for frosting to avoid making it too salty. It should be softened but not melted.
Powdered sugar – Sweetens and helps stabilize the frosting.
Cocoa powder – Adds the chocolate flavor.
Heavy cream – Stabilizes the frosting. Use only as much as needed to achieve the desired consistency.
Vanilla extract
Salt – A pinch of salt balances the sugary sweetness in the frosting.

How To Make Chocolate Zucchini Cake

I think the hardest part of making this cake is waiting for it to cool before frosting! The printable instructions can be found in the recipe card below.

Dry chocolate cake ingredients in a bowl

Adding egg and vanilla to creamed butter and sugar

Prep. Preheat the oven to 350F. Grease the cake pan or line it with parchment paper.
Make the batter. Whisk the dry ingredients together. In a separate bowl, whisk the sugar, oil, butter, and buttermilk. Mix in the eggs and vanilla. Slowly incorporate the dry ingredients to the wet mixture, mixing until just combined. Gently stir in the zucchini, folded by the chocolate chips.

Stirring grated zucchini into chocolate cake batter

Adding chocolate chips to chocolate cake batter

Bake. Transfer the batter into the prepared pan. Bake for 35-40 minutes. A toothpick inserted in the center should come out clean or with a few moist crumbs. Cool completely before frosting.

Make the frosting. Beat the butter until smooth and creamy. Sift in the powdered sugar and cocoa powder on low spread. Add the heavy cream, vanilla, and salt. Beat on high until the frosting is fluffy and smooth. If it’s too thick, add a tablespoon of extra heavy cream.
Frost the cake. Once the cake is completely cool, spread an even layer of buttercream on top with a spatula. Cut into slices and enjoy.

Tips & Variations

Here are a few key tips for making chocolate zucchini cake, as well as a few ways to customize it.

Leave some moisture in the zucchini. Do not completely dry the zucchini after squeezing, some moisture is essential for a moist cake.
Try mini chocolate chips. You can use mini chocolate chips for more even distribution or swap them for dark, milk, or white chocolate chips.
Add some nuts. Walnuts or pecans can be folded into the batter along with the chocolate chips for added crunch and flavor.
Frosting options. Add a pinch of espresso powder to the frosting for a richer chocolate flavor or swap the buttercream for ganache if you prefer a glossy finish.
Turn them into cupcakes. This recipe can easily be adapted to make chocolate zucchini cupcakes. Just follow the instructions as listed, pour the batter into cupcake liners, and adjust the bake time to 18-22 minutes.

A fork in a slice of chocolate zucchini cake

Proper Storage

Room temperature. Store leftover chocolate zucchini cake tightly covered at room temperature for up to 3 days.
Fridge. For longer storage, keep the cake in the refrigerator for up to 5 days.
Freezer. The cake (frosted or unfrosted) freezes well. Wrap tightly in plastic wrap, then aluminum foil, and freeze for up to 3 months. Thaw in the fridge overnight before serving.