Cold Tuna Salad Casserole Recipe: Crispy Topped Comfort in One Dish

This cold tuna salad casserole delivers restaurant-quality comfort without the fuss of baking—just layer, chill, and serve. The secret lies in the crispy breadcrumb topping that forms while refrigerating, creating a satisfying crunch over creamy tuna filling.

I developed this recipe for busy weeknights when I craved a hearty dish that still felt special, and it never fails to disappear from the table. What sets this apart is the balance of textures: tender tuna, creamy dressing, and that irresistible crispy top that forms naturally during chilling.

The dish stays fresh for days, making it perfect for meal prep or potlucks. Traditional techniques like proper layering and binding with mayo ensure it holds together beautifully, while modern twists like avocado or citrus add brightness.

By the time you slice into this casserole, you'll have a dish that's foolproof yet impressive—creamy tuna filling with a golden, crispy crust that holds up perfectly when served chilled. The flavors meld beautifully as it rests, making every bite richer and more satisfying than the last.

Serve with crusty bread or a simple green salad for a complete meal. Here's how to make it shine.

Ingredients for cold tuna salad casserole

Six ingredients for the filling, six for the crispy top—just layer and chill.

The tuna makes this dish shine, so grab high-quality canned tuna—none of that mushy stuff. I always pick Wild Planet or StarKist for the best texture. The Greek yogurt adds creaminess without making it too heavy, and if you're watching calories, non-fat works just fine. For the crispy topping, Panko is non-negotiable—it stays crispy while regular breadcrumbs get soggy. Fresh dill and avocado add brightness, but if you're short on time, skip them—the dish still tastes amazing. The key to that perfect crunch is mixing the breadcrumbs with Parmesan and olive oil before topping.

No mayo? Greek yogurt plus a splash of lemon juice does the trick—it's lighter but still creamy. Running out of Dijon? Yellow mustard works too, though it's a bit sharper. If avocado isn't in season, diced cucumber or red bell pepper adds freshness. The lemon juice is non-negotiable for that bright tang, but if you're out, a pinch of citric acid in a pinch. For the crispy topping, if you don't have Parmesan, crushed cornflakes or matzo meal work in a bind—just add an extra tablespoon of olive oil to keep it crispy.

This casserole tastes even better the next day, so make it ahead if you can. Store it in an airtight container in the fridge for up to 4 days. The crispy top stays perfect if you press plastic wrap directly on it before sealing. For potlucks, portion it into individual containers—it holds together beautifully and looks impressive. Freezes for 2 months if you want to prep ahead for busy weeks. Just let it sit at room temperature for 30 minutes before serving to bring out those flavors.

Step-by-step instructions for cold tuna salad casserole

Here's how to assemble this creamy, crispy masterpiece with minimal effort.

In a large mixing bowl, gently flake the drained 2 cans canned tuna in water with your fingers or a fork, breaking it into small, even pieces. The tuna should remain tender but still hold its shape slightly. Add the 1 cup mayonnaise, 0.5 cup plain Greek yogurt, 2 tbsp lemon juice, and 1 tbsp Dijon mustard to the bowl and mix thoroughly with a spoon or spatula until completely combined.

Next, finely chop the 2 whole celery stalks and 0.25 cup red onion (I like to use a food processor for this step to get an even, fine texture). Add these to the tuna mixture along with the 1 tsp salt and 0.5 tsp black pepper. If using, dice the 1 whole avocado into small pieces and fold it in gently at the very end to preserve its texture. Mix everything together until evenly distributed—you should have a smooth, creamy base that's ready for the crispy topping.

Preheat your oven to 375°F while you prepare the casserole. Lightly grease a 9x13-inch baking dish with nonstick spray or a thin layer of olive oil to prevent sticking. Spread the tuna salad mixture evenly across the bottom of the dish, pressing down gently with a spatula to create a smooth, even layer. This helps the crispy topping adhere better and ensures even cooking.

For extra flavor, sprinkle the 2 tbsp fresh dill evenly over the tuna mixture. The dill adds a bright, herby note that balances the richness of the tuna and mayo. Once the dill is distributed, give the mixture one final gentle stir to incorporate it fully.

In a medium bowl, combine the 1.5 cups panko breadcrumbs, 0.5 cup shredded Parmesan cheese, and 1 tbsp olive oil. Stir with your hands or a fork until the breadcrumbs are evenly coated with oil and Parmesan—this creates a golden, flavorful crust. If you like, you can add a pinch more salt to the topping for extra seasoning, but the Parmesan and panko already provide plenty of flavor.

Spread the breadcrumb mixture evenly over the tuna salad in the baking dish, pressing down lightly with the back of a spoon or your fingers to help it stick. The topping should cover the entire surface of the casserole without gaps. For a more rustic look, you can create a simple crisscross pattern with the back of a fork before baking.

Place the casserole in the preheated 375°F oven and bake for 20-25 minutes, or until the topping is deep golden brown and the edges are bubbling. The center should still be slightly soft—this ensures the tuna salad stays creamy and not overcooked. If the topping browns too quickly, tent the dish with aluminum foil for the last 5-10 minutes of baking to prevent burning.

I like to check for doneness by gently pressing the center with a spoon—it should spring back slightly rather than feel firm. Once the topping is crispy and golden, remove the casserole from the oven and let it rest for 5-10 minutes before serving. This resting time allows the flavors to meld and the topping to set slightly, making it easier to slice and serve.

Use a sharp knife to cut the casserole into 6 equal squares (or rectangles, if you prefer). The crispy topping will hold together beautifully, and the creamy tuna salad will peek out from underneath. Serve immediately while the topping is still warm and crispy—it's even better the next day, though!

Pair this casserole with a simple side salad or crusty bread to soak up any extra tuna salad. The combination of creamy, tangy tuna and the golden, crunchy topping makes this dish a crowd-pleaser for any occasion. Store leftovers in the refrigerator for up to 3 days, though I doubt it will last that long!

Storing and reheating your leftovers

Refrigerator Storage

This casserole stays fresh in the fridge for up to 4 days when stored in an airtight container. I always press plastic wrap directly on the crispy topping before sealing to preserve that satisfying crunch.

The flavors actually deepen overnight, making it perfect for meal prep—just assemble in the morning and enjoy for lunch or dinner. 🥫

Freezer Prep Tips

For longer storage, freeze individual portions in quart-sized freezer bags with 1 inch headspace to prevent expansion cracks. Thaw overnight in the fridge for best texture—microwaving can make the topping soggy. I like to freeze it after baking so the crispy layer stays intact. 🧊

Reheating Methods

For stovetop reheating, cover the casserole with a damp paper towel and warm on low heat for 10-15 minutes. The gentle heat keeps the topping crispy while warming the filling.

For microwave reheating, use 50% power for 2-minute intervals, stirring between each. Add a splash of water if it looks dry.