Double Chocolate Zucchini Cake

Published: Aug 10, 2020 · Modified: Mar 22, 2026 by Leanne

Double Chocolate Zucchini Cake is fudgy and moist, filled with cocoa, studded with dark chocolate chips and topped with a creamy chocolate avocado frosting. It tastes a little indulgent yet it's filled with wholesome ingredients. Your family will never know they're eating their veggies!

If you love this chocolate cake with zucchini, you'll also love these chocolate zucchini cupcakes! (These almond flour zucchini muffins are definitely worth a try too!)

Overhead and close up view of chocolate zucchini cake topped with frosting and cut into squares.

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*This post was originally published in May 2017 and has been updated with new text and photos and a few tweaks to the recipe.

When I first started Crumb Top Baking this was definitely my most popular recipe, and it's still one of my most requested desserts whenever I'm asked to make one.

So, when zucchini season rolls around, this chocolate zucchini cake with apple sauce tops my list to make!

Side view of pieces of chocolate zucchini cake arranged on a white sheet of parchment paper.

Why you'll love this recipe

It's a double chocolate zucchini cake with cocoa and dark chocolate chips. So it tastes like a rich and decadent chocolate cake, but the ingredient list is far from indulgent.
It's not an overly sweet cake, containing very little refined sugar. It's sweetened with honey, coconut sugar and some dark chocolate chips. It's loaded with cocoa flavor, which I think makes up for the lack of sweetness.
There isn't any butter or a large quantity of oil in this recipe. The fats come from the flax meal and extra virgin olive oil.
The cake is simple to make (even though the ingredient list is long) and stores well in the refrigerator, so it can easily be made in advance.

Overhead view of ingredients to make healthy chocolate zucchini cake arranged in individual bowls.

Details on a few ingredients

Zucchini - The recipe calls for one cup of grated zucchini, which may seem like a lot, but it has a mild flavor so it doesn't affect the taste of the cake. It adds moisture and texture, as well as some added nutrition such as fibre.
Apple sauce - Unsweetened apple sauce also adds moisture and extra fibre to this cake. It's often used as a replacement for butter in baking.
Whole wheat flour - This is my preferred flour to keep this cake on the healthier side. It's also more absorbent than white flour, so it works well with all the moisture in this cake.
Flax meal - Ground flax seed is concentrated with oil so a tablespoon is used to compensate for the small amount of oil added to the cake.

Collage of 4 images showing how the batter comes together in a glass bowl and ends up spread out into an 8-inch square pan.

How to make chocolate cake with zucchini

Step 1: In a medium-sized bowl, whisk or sift together your dry ingredients.

Step 2: In a separate large bowl, whisk together the egg with the other wet ingredients.

Step 3: Add the dry ingredients to the wet ingredients and stir until combined. Gently mix in the zucchini and chocolate chips. Don't over mix.

Step 4: Spread the batter out into an 8-inch square pan that has been greased and lined with parchment paper. Bake for 25-27 minutes. Cool on a wire rack.

How to make chocolate avocado frosting

Step 5: Add ripe avocado, cocoa, maple syrup and nut milk to a medium sized bowl or blender and beat with an electric mixer or blend on high until smooth and creamy. (To minimize the cocoa dust, you can add the cocoa in small portions and beat after each addition).

Step 6: Spread the frosting over the cooled cake and cut into squares.

Collage of 2 images showing the frosting ingredients in a bowl and the frosting being spread onto the cake.

Storage instructions

If your zucchini cake is unfrosted, you can wrap it in plastic wrap or store it in an airtight container at room temperature. It should last for 2-3 days.

If the cake is frosted, store it in an airtight container in the fridge and enjoy within 4-5 days.

Frequently asked questions

Do you need to peel zucchini for cake recipes?

No need to peel. The skin is very thin so while you will see flecks of green in the cake, it really isn't noticeable otherwise. Just be sure to choose zucchini that are free of dents or scratches on the skin, and wash well before grating.

Should you drain or squeeze water out of the zucchini for this cake?

While some recipes call for draining or pressing the water out of zucchini before adding it to cake batter, this recipe accounts for the added moisture so there's no need to do that. In fact, if you do it, the cake may be too dry.

Can zucchini cake be frozen?

The unfrosted cake can be frozen. Just wrap it tightly in plastic wrap and place in an airtight container. Store in the freezer for up to 3 months. Let it defrost in the plastic wrap at room temperature before frosting. I don't recommend freezing the frosted cake as I'm not sure how the avocado frosting will hold up once frozen and defrosted.

Overhead view of chocolate avocado frosting spread out on top of the cake.

Recipe tips and substitutions

I recommend shredding your zucchini using the larger shredding holes of a box grater (cheese grater). Don't grate it with the smaller holes as the zucchini will be too finely shredded and will release too much moisture into the cake.
I used dutch-processed cocoa in the cake recipe. I haven't tested the cake with natural cocoa. The frosting, on the other hand, works with both kinds of cocoa.
You can make this recipe in a 9x5 inch loaf pan. Just increase the baking time by 7-10 minutes, or until a toothpick inserted in the middle comes out clean.
While I make the chocolate avocado frosting all the time with my handheld electric mixer, I find blending it in the smoothie cup that came with my blender results in the creamiest and smoothest frosting. It's also a little less messy.
This zucchini cake with chocolate chips isn't overly sweet, but if you'd like to make it sweeter, try adding some sweetened coconut flakes or chocolate shavings to the top of the frosting.