Chocolate Zucchini Cake

This chocolate zucchini sheet cake is fudgy, tender, and deeply chocolatey, with tiny flecks of shredded zucchini that melt into the crumb and keep every square moist without a pronounced veggie taste.

It comes together in about 45 minutes and bakes in a 9×13″ pan — an easy weeknight dessert or potluck pan that you can top with a quick chocolate whipped cream and slice into crowd-pleasing squares.

Why You’ll Love This Cake

A simple 9×13 sheet yields a reliably moist, fudgy cake that sneaks in 3 cups of shredded zucchini while keeping a rich chocolate profile. If you like fudgy chocolate bars and portable desserts, try Chewy Chocolate Chip Blondies with Oatmeal Cookie Streusel for another crowd-pleasing bake.

This recipe is forgiving: control the texture by draining the zucchini well, follow the simple mixing order, and top the cooled cake with the light chocolate whip for a dessert that feels special without extra effort.

How to Make the Cake

1. Preheat the oven to 350°F and lightly grease a 9×13″ pan (line with parchment paper if desired). Position a rack in the center of the oven.
2. In a large bowl, whisk together the dry ingredients: 2 cups flour, 3/4 cup unsweetened cocoa powder, 2 teaspoons baking soda, 3/4 teaspoon baking powder, 3/4 teaspoons salt, and 2 cups granulated sugar until evenly combined.
3. In a separate bowl, whisk the wet ingredients: 1 cup buttermilk, 2 eggs (room temperature), and 1 1/2 teaspoons vanilla until smooth.
4. Prepare the zucchini: shred about 3 cups shredded zucchini (about 2 small or 1 large), then drain it well (see ‘Drain the Zucchini Well’ section). Fold the squeezed zucchini into the wet ingredients.
5. Pour the wet mixture into the dry ingredients and stir gently until just combined — stop as soon as there are no streaks of flour. Overmixing will stiffen the crumb.
6. Transfer the batter to the prepared 9×13″ pan and smooth the top with a spatula so it bakes evenly.
7. Bake at 350°F for about 30 minutes. Check doneness by inserting a toothpick into the center — it should come out with a few moist crumbs (not wet batter) and the edges should begin to pull away slightly from the pan.
8. Remove the cake from the oven and let it cool completely in the pan on a wire rack before topping.
9. To make the chocolate whipped cream topping: in a chilled bowl, whip 1 1/2 cups heavy whipping cream to soft/medium peaks, then gradually add 2/3 cup powdered sugar, 3 tablespoons unsweetened cocoa powder, and 1 teaspoon vanilla. Continue whipping to medium peaks, taste and adjust sweetness, then chill briefly if needed.
10. Spread the chocolate whipped cream over the cooled cake and slice into squares. Refrigerate any leftovers.

Drain the Zucchini Well

Shredded zucchini holds a surprising amount of water that can make this cake gummy if not removed. After grating, gather the zucchini in a clean kitchen towel or several layers of cheesecloth, twist the cloth, and press over the sink or into a bowl until the stream of liquid stops.

You’re aiming to remove excess free liquid — not to dry the zucchini to a crumbly state. When it’s properly drained you’ll still have moist shreds that blend into the batter and keep the cake tender.

• Use a medium grater for tender shreds that disappear into the crumb.
• Squeeze until only a few tablespoons of liquid run out — this prevents sogginess while keeping moisture.
• No need to peel the zucchini first; the peel adds color and not much texture once shredded.

Finish with Chocolate Whip

Whip the topping just to medium peaks so it’s light but stable enough to spread. Start with a chilled bowl and beaters if possible — this helps the cream thicken faster.

Add the powdered sugar, unsweetened cocoa powder, and vanilla after the cream has thickened to soft peaks; then whip to medium peaks and chill briefly if it feels too soft to spread.

• Chill the mixing bowl and beaters for best results.
• Add the sugar and cocoa gradually to avoid lumps and to taste for sweetness.
• If you need a sturdier topping for piping, fold in a small amount of stabilized whipped cream or chill the whipped cream well before piping.

Save This Recipe

More Recipes

Frequently Asked Questions

Final Notes

This chocolate zucchini sheet cake is a great make-ahead dessert: freeze the unfrosted pan, top after thawing, and slice into neat squares for parties or school treats.

If you want another fudgy, portable chocolate bake, the Chewy Chocolate Chip Blondies recipe linked above is a delicious alternative.