My blackberry dump cake with frozen berries recipe is easy and delicious! This old-fashioned cobbler is made by layering frozen blackberries, sugar, cake mix, and butter in a 9×13 baking dish, then baking until the top turns into a golden-brown crumble. And since you don’t need to thaw the berries—you can use them frozen right from the freezer—this recipe is super simple, making it perfect for beginner cooks who need to make a dessert to feed a crowd. This cobbler is also super versatile, so it would be great for a summer holiday like the 4th of July, or even Thanksgiving, Christmas, Easter, Mother’s Day—or any day! If you want to learn how to make blackberry dump cake with frozen berries, follow my step-by-step directions and watch the video below!
Blackberry Dump Cake with Frozen Berries
Ingredients
- 30 oz frozen blackberries (6 cups, 850g)
- 1 15.25 oz box white cake mix
- 2 sticks butter, unsalted (226g)
- 3/4 cup white sugar (160g)
- 4 Tablespoons cornstarch (40g)
- *Optional but highly recommended:
- 3 Tablespoons lemon juice
- 1/8 teaspoon salt
Instructions
- Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish with butter.
- Add the frozen blackberries to the prepared baking dish and spread them into an even layer. Note that you don't need to thaw them first—you can use them directly from the freezer.
- Sprinkle the sugar, cornstarch, salt, and lemon juice over the berries. Toss everything together gently until the berries are evenly coated, then spread the mixture back into an even layer.
- Sprinkle the dry white cake mix evenly over the blackberry mixture.
- Use a fork to gently level the cake mix into an even layer without stirring it into the fruit.
- Slice the cold butter into very thin pats and arrange them evenly across the entire surface of the cake mix, filling in any large gaps with small pieces of butter.
- Bake uncovered at 350°F (175°C) for an hour and 10 minutes (70 minutes total), or until the topping is golden brown and the blackberry filling is bubbling around the edges.
- Let the dump cake cool for 20–30 minutes before serving. Enjoy warm on its own or with vanilla ice cream or whipped cream.
Recipe Review
My blackberry dump cake with frozen berries recipe was a huge success. This cobbler has plenty of blackberry flavor with a balance of sweetness, tartness, and just a hint of bitterness from the seeds. The lemon juice, although optional, brightened the fruit without making the dessert taste lemony, and I thought the 3/4 cup of sugar was just enough to balance the natural tartness of the berries without making the dump cake overly sweet.
Although there was some bitterness from the seeds, the cakey, buttery crumble was the perfect counterbalance, mellowing out the bitterness so that it became an interesting background element rather than an annoying distraction. Even if you normally avoid blackberries because of the seeds, I think you would probably still like this dessert.
I really liked the texture as well. The blackberries cooked through beautifully, some holding their shape while others fell apart into a jammy, pie filling-like consistency. The cake mix topping was crispy, crumbly, and amazingly buttery, contrasting nicely with the fruit layer underneath.
In fact, I was very surprised by how well this recipe turned out. I was a bit nervous about using frozen blackberries without thawing them first, but I was pleasantly surprised by how they thawed out and cooked down in the oven as the topping turned golden brown. I was afraid that maybe the fruit layer would be watery, or that the crumble topping might burn while some of the berries stayed partially frozen, but none of my fears came true.
Honestly, there isn’t really anything that I’d change about this recipe—I thought the flavor and texture were on point, not only meeting but also exceeding my expectations. I’ve made a lot of variations of old-fashioned blackberry cobbler with pie crust, which I love, so I honestly didn’t think I’d like the dump cake version as much as I did. The only tweak you might want to make is adding some spices—maybe 1/4 teaspoon cinnamon or 1/8 teaspoon nutmeg, but I usually use minimal spices when using fresh or frozen fruit because I don’t want to cover up the amazing flavor.
This blackberry dump cake using frozen blackberries would be perfect for a beginner cook who wants to make a quick and easy dessert without rolling out pie dough or prepping fruit. And since it’s made in a 9×13 dish, it’s perfect for feeding crowds, especially on a holiday like Memorial Day, Labor Day, Thanksgiving, or even just a large gathering for a picnic or Sunday dinner. If you make this recipe, I know you’ll love it! Best of all, you can make this recipe any time of the year because frozen blackberries are readily available and don’t need to be thawed before baking.
Blackberry Dump Cake with Frozen Berries FAQ
Bake the blackberry dump cake at 350°F (175°C) for about 70 minutes, uncovered. It’s done when the topping is golden brown and the blackberry filling is bubbling around the edges. Let it cool for 20 to 30 minutes before serving so the filling has time to thicken.
This recipe makes about 8 servings, so it’s a great dessert for family dinners, potlucks, holidays, and other gatherings. If you’re trying to feed a larger crowd, you can cut it into 12 or maybe even 16 small portions.
No—you don’t have to thaw the frozen berries before using them in this recipe. If they are thawed, that’s fine—it won’t affect the outcome of the recipe.
You’ll need 30 ounces (850 grams), or about 6 cups, of frozen blackberries—this is the perfect amount for having a good layer of fruit on the bottom without sacrificing the crispy top. If your grocery store sells 16 oz bags, go ahead and use 2 for a total of 32 oz—this recipe is easy and forgiving, so a little more fruit won’t hurt it.
Yes—but with a caveat. You could grate frozen butter and sprinkle it over the top, or pour melted butter over the cake mix. However, I prefer slicing the butter because it helps cover the cake mix more evenly, resulting in a crisp, golden topping.
The most important thing to remember is to make sure the butter is distributed as evenly as possible over the dry cake mix. If there are large areas without butter, those spots may remain dry after baking instead of forming a buttery crumble topping.
Yes, this recipe has plenty of blackberry seeds because it uses whole blackberries. While you may notice a slight bitterness from the seeds, the cakey, buttery topping helps balance the flavor and keeps it from becoming overwhelming.
Yes! As the butter melts into the dry cake mix during baking, it creates a crispy, buttery crumble topping that’s perfectly golden brown. The contrast between the crisp topping and the soft blackberry filling is one of the best parts of this dessert.
Store leftover blackberry dump cake in the refrigerator for up to 3–4 days—to keep the topping crispy for as long as possible, store it loosely covered so that excess moisture doesn’t become trapped and soften the crumble topping. For more general food storage recommendations, you can also check the USDA FoodKeeper, which provides storage guidelines for hundreds of foods.
Yes. Allow the dump cake to cool completely, then wrap it tightly or transfer it to an airtight container before freezing. It will keep well for up to 3 months. Thaw it overnight in the refrigerator—uncovered so that the crumble doesn’t get soggy—before reheating and serving.
Other Dump Cake Recipes:
If you like cake mix cobblers, take a look at these other desserts:
Blackberry Dump Cake with Pie Filling – This 3-ingredient cobbler has all the same flavor but with a slightly crispier crust.
Peach Dump Cake with Canned Peaches – A simple version of a southern classic, canned fruit makes this cobbler super easy to make.
Strawberry Dump Cake with Cake Mix – Pie filling, cake mix, and butter make this 3-ingredient cobbler a winner.
