This chocolate zucchini loaf cake with fudgy chocolate icing is rich, moist, and full of deep chocolate flavor — no one will ever guess it's packed with zucchini.
For a classic chocolate cake without zucchini, try my chocolate sheet cake with chocolate cream cheese frosting, or if you want to use up sourdough discard, my sourdough chocolate cupcakes are a favorite.
Quick Look: Chocolate Zucchini Loaf Cake
⏱️ Ready In: About 1 hour 20 minutes
🔥 Bake Time: 45–55 minutes at 350°F
🍽️ Makes: 10 slices
✨ Calories: Approximately 555 per slice
🥄 Main Ingredients: Grated zucchini, cocoa powder, brown sugar, chocolate icing
🌿 Dietary Info: Vegetarian (easily dairy-free and gluten-free)
💛 Why You'll Love It: A deeply chocolatey, fudgy loaf with a glossy chocolate icing — and a sneaky way to use up summer zucchini.
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Why You'll Love This Recipe
- Deep chocolate flavor. Cocoa (and optional espresso powder) make it taste rich, not vegetal, like my chocolate peppermint kiss cookies. If you love chocolate desserts, make sure you try my raspberry chocolate tart!
- Incredibly moist. Grated zucchini keeps the crumb soft and fudgy for days, the same trick as my healthy chocolate zucchini bread.
- That glossy chocolate icing. A shiny, sweet topping that sets like a bakery loaf.
- No mixer needed. The batter comes together with just a whisk and a bowl.
- A sneaky way to use zucchini. A delicious use for the summer surplus, like my spiced zucchini snack cake.
Jump to:
- Quick Look: Chocolate Zucchini Loaf Cake
- Why You'll Love This Recipe
- Ingredients
- Easy Substitutions & Variations
- How to Make Chocolate Zucchini Loaf Cake
- Expert Tips
- What Makes This Recipe Special?
- Chocolate Zucchini Loaf Cake FAQs
- Chocolate Zucchini Loaf Cake Troubleshooting Guide
- Storage
- Other Cake Recipes to Consider
- Chocolate Zucchini Loaf Cake With Fudgy Chocolate Icing
Ingredients
For the cake
- All-purpose flour: The structure of the loaf.
- Unsweetened cocoa powder: The main source of chocolate flavor.
- Baking soda + baking powder: Your lift.
- Kosher salt: Balances the sweetness.
- Espresso powder (optional): Deepens the chocolate flavor without tasting like coffee — the same trick I use in my chocolate cinnamon rolls with espresso cream cheese icing and coffee and walnut loaf cake.
- Brown sugar: Adds moisture and caramel depth.
- Neutral oil: Keeps the loaf moist for days.
- Eggs + vanilla: Bind and enrich the batter.
- Whole milk or buttermilk: Loosens the batter.
- Grated zucchini: The secret to a soft, fudgy crumb — don't wring it out.
- Mini chocolate chips (optional): For melty chocolate pockets.
For the chocolate icing
- Unsalted butter, unsweetened cocoa powder, powdered sugar, boiling water, and vanilla: Whisked into a glossy, pourable chocolate icing.
See recipe card for quantities.
Easy Substitutions & Variations
- Buttermilk or milk: Either works; whole milk keeps it just as moist.
- Brown sugar: Swap for granulated in a pinch, though brown sugar adds richness.
- Espresso powder: Optional — leave it out and the loaf is still deeply chocolatey.
- Gluten-free: A 1:1 gluten-free blend works well (slightly softer texture).
- Double chocolate: Add extra chocolate chips, like my sourdough double chocolate muffins.
- Nutty chocolate loaf: Fold in chopped walnuts or pecans for crunch.
- More zucchini bakes: Turn the same idea into my sourdough zucchini muffins or, for pure fudge, my fudgy zucchini brownies.
- Mini loaves or muffins: Bake in mini pans or muffin tins (reduce the bake time).
- Glaze instead of icing: Skip the thick icing and drizzle with a simple powdered sugar glaze, like the finish on my chocolate chunk banana bread.
How to Make Chocolate Zucchini Loaf Cake
Note: I bake by weight for accuracy. Cup measurements are approximate and may vary depending on how you scoop.
Step 1: Make the batter: Whisk the dry ingredients in one bowl. In a large bowl, whisk the brown sugar, oil, eggs, vanilla, and milk until smooth, then stir in the grated zucchini and chocolate chips. Fold in the dry ingredients until just combined.
Step 2: Bake the loaf: Pour into a lined 8x4 loaf pan and bake at 350°F for 45–55 minutes, until a toothpick comes out with a few moist crumbs. Cool completely.
Step 3: Make the icing: Whisk the boiling water and cocoa until smooth, then add the butter and vanilla and beat in the powdered sugar gradually until glossy and pourable.
Step 4: Ice and serve: Spread the icing generously over the cooled loaf and let it set 15–20 minutes before slicing.
Weigh your ingredients! Using a kitchen scale ensures your measurements are accurate, which is key for consistent results in baking. It takes the guesswork out of measuring and helps your loaf turn out exactly as intended every time.
Expert Tips
- Don't squeeze the zucchini. Its natural moisture is what keeps the cake extra soft and fudgy.
- Grate it finely. Fine shreds disappear into the batter so there are no stringy bits.
- Sift the cocoa and powdered sugar for the icing. This keeps the icing smooth and glossy with no lumps.
- Don't overmix the batter. Fold just until combined for a tender crumb.
- Ice a fully cooled loaf. Warm cake will make the icing run instead of setting.
What Makes This Recipe Special?
The magic of this loaf is that it tastes like a rich, fudgy chocolate cake while quietly using up a couple cups of zucchini. The zucchini brings moisture without flavor, so the cake stays soft for days, and the cocoa (plus a little espresso powder) makes the chocolate taste deep and grown-up. Topped with glossy chocolate icing, it looks and tastes like a bakery loaf.
If you love a deeply chocolate dessert, you're in good company on the blog. My sourdough double chocolate muffins bring the same richness in muffin form, and my chocolate sour cream pound cake is another moist, sliceable chocolate loaf.
Chocolate Zucchini Loaf Cake FAQs
No — the skin is tender and disappears into the cake as it bakes. Just grate it whole
No. The moisture is what keeps this loaf soft and fudgy, so add it grated but not wrung out.
Not at all — the cocoa and chocolate completely hide it. It just keeps the cake moist.
Yes — use a 1:1 gluten-free flour blend. The texture will be a touch softer but still delicious.
Yes — divide the batter into muffin tins or mini loaf pans and reduce the bake time, checking early with a toothpick.
Chocolate Zucchini Loaf Cake Troubleshooting Guide
| Problem | Cause | Fix |
|---|---|---|
| Dense or gummy loaf | Overmixed batter or zucchini wrung out then extra liquid added. | Fold just until combined and leave the zucchini's moisture in. |
| Wet center | Underbaked. | Bake until a toothpick comes out with just a few moist crumbs. |
| Lumpy icing | Cocoa or powdered sugar not sifted. | Sift both before mixing for a smooth, glossy icing. |
| Icing too thick / too thin | Needs adjusting. | Add a splash more boiling water to loosen, or more powdered sugar to thicken. |
| Icing ran off | Loaf was still warm. | Cool the loaf completely before icing. |
Storage
- Store in an airtight container at room temperature for up to 3 days, or refrigerate for up to 5 days.
- Freeze (whole or in slices) wrapped tightly for up to 2 months; thaw in the fridge, then bring to room temperature before serving.
Other Cake Recipes to Consider
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Chocolate Zucchini Loaf Cake With Fudgy Chocolate Icing
Equipment
- 8x4-inch loaf pan
- Parchment Paper
- Mixing bowls (medium and large)
- Whisk
- Spatula or wooden spoon
- Measuring cups and spoons (or a kitchen scale for accuracy)
- Grater (for zucchini)
- Wire rack (for cooling)
- Toothpick or cake tester
- Small offset spatula or spoon (for spreading icing)
Ingredients
For the cake:
- 210 g all-purpose flour 1 ¾ cups
- 45 g unsweetened cocoa powder ½ cup
- 1 teaspoon baking soda
- ½ teaspoon baking powder
- ½ teaspoon kosher salt
- 1 teaspoon espresso powder optional, enhances chocolate flavor
- 200 g brown sugar 1 cup, packed
- 120 ml neutral oil ½ cup
- 2 large eggs
- 1 teaspoon vanilla extract
- 120 ml whole milk or buttermilk ½ cup
- 260 g grated zucchini about 2 cups, loosely packed
- 85 g mini chocolate chips ½ cup, optional
For the chocolate icing:
- 90 g unsalted butter ¼ cup or ½ stick
- 40 g unsweetened cocoa powder ½ cup
- 360 g powdered sugar 3 cups
- 6 tablespoon boiling water
- 2 teaspoon vanilla extract
Instructions
- Prep the pan: Preheat oven to 350°F (175°C). Grease and line an 8x4-inch loaf pan with parchment paper.
- Mix the dry ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking soda, baking powder, salt, and espresso powder.210 g all-purpose flour, 45 g unsweetened cocoa powder, 1 tsp baking soda, ½ tsp baking powder, ½ tsp kosher salt, 1 tsp espresso powder
- Make the batter: In a large bowl, whisk together the brown sugar, oil, eggs, vanilla, and milk until smooth and emulsified.200 g brown sugar, 120 ml neutral oil, 2 large eggs, 1 tsp vanilla extract, 120 ml whole milk or buttermilk
- Fold in zucchini: Stir in the grated zucchini and chocolate chips (if using) until evenly distributed.260 g grated zucchini, 85 g mini chocolate chips
- Combine & bake: Add the dry ingredients to the wet and fold gently until just combined. Pour the batter into the prepared pan and smooth the top. Bake for 45–55 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs.
- Cool the cake: Let the loaf cool in the pan for 10–15 minutes, then transfer to a wire rack to cool completely.
- Make the chocolate icing: In a medium bowl, whisk together the boiling water and cocoa powder until smooth. Add the softened butter and vanilla, then beat in the powdered sugar gradually until smooth and glossy. The icing should be thick but pourable—add a splash more water if needed.90 g unsalted butter, 40 g unsweetened cocoa powder, 6 tbsp boiling water, 2 tsp vanilla extract, 360 g powdered sugar
- Ice the cake: Once the cake is fully cool, spread the icing generously over the top and let it set for 15–20 minutes before slicing.
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