Easy Tuna Casserole Recipe – Great Cheap Dinner Idea

Let me show you my favorite easy tuna casserole recipe that has saved me countless times. It definitely sits at the top of my quick and cheap dinner ideas list. It is especially great if you need to use up some leftover mashed potatoes.

Watch my video below for a simple, step-by-step recipe for creating this delicious and easy tuna casserole. If you enjoy it, don’t forget to like and subscribe for more easy and tasty recipes!

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Why I Keep Making This Tuna Casserole

I like this recipe because it’s simple, filling, and costs less than $10 for the whole dish. The layers of potatoes and tuna with cheese on top taste great together, and it takes less than an hour to make from start to finish.

My family actually eats this without complaining, which is a win in my book. It’s become one of my regular meals when I need something reliable that won’t break the bank.

Ingredients You’ll Need

Here’s what to grab at the store:

• 2 cans (5 ounces each) of tuna in water, drained
• 1 medium onion, chopped
• 5 medium potatoes
• 2 tablespoons tomato paste
• 3/4 cup milk
• 20 grams of butter
• 60 grams of mozzarella cheese, grated
• Olive oil or regular cooking oil
• Salt and black pepper

Top Tip: Get chunk light tuna instead of solid white albacore. It’s cheaper, breaks up better in the casserole, and tastes just as good in this recipe.

Equipment You’ll Need

Just the basics:

• Pot for boiling potatoes
• Frying pan
• Potato masher
• Casserole dish (9×13 inches works well)
• Mixing bowls
• Wooden spoon

How to Make This Tuna Potato Casserole

Here’s how to put it all together step by step.

Making the Tuna Part

This is the flavorful part of the casserole that gives it its main taste.

Step 1: Heat some oil in a pan and cook the chopped onion for about 5-7 minutes until it gets soft.

Step 2: Add your drained tuna to the onions. Break it up with your spoon as it warms.

Note: Make sure to drain the tuna really well, or your casserole might get watery.

Step 3: Mix 2 tablespoons of tomato paste with about 4 tablespoons of hot water in a small bowl.

Step 4: Add this tomato mix to the tuna and onions, stir it all together, then take it off the heat.

Making the Potato Part

The potatoes make this dish filling and give it a nice creamy texture.

Step 5: Cut your potatoes into chunks and boil them in salted water for about 10-15 minutes until you can easily stick a fork in them.

Step 6: Drain the potatoes and mash them until they’re smooth.

Step 7: Add the butter, salt, and pepper to the hot potatoes and mix until the butter melts.

Step 8: Pour in the milk and stir until it’s all mixed in.

Top Tip: Yellow potatoes like Yukon Golds make better mashed potatoes for this recipe than russets. They’re creamier and less likely to get gluey.

Putting It All Together

Now you’ll layer everything to create the casserole.

Step 9: Spread half of your mashed potatoes on the bottom of your casserole dish.

Step 10: Put half of the tuna mix on top of that.

Step 11: Add the rest of the potatoes as another layer.

Step 12: Spread the rest of the tuna on top and cover it all with the grated cheese.

Step 13: Bake at 350°F (180°C) for 25-30 minutes until the cheese melts and gets a bit golden.

Did You Know? If you let the casserole sit for about 5 minutes after taking it out of the oven, it’s easier to cut into neat servings.

Related Recipe: If you liked this tuna and potato dish, try my One-Pan Meatballs with Mashed Potatoes and Cheese for another easy, hearty meal.

Adding More Flavor

The basic recipe tastes good, but these easy additions make it even better.

Adding 1/2 teaspoon of garlic powder to the potato mix gives it more flavor. A tablespoon of lemon juice in the tuna mixture makes the flavor brighter.

Try mixing half mozzarella and half cheddar for the topping. You’ll get more flavor but still have that nice melty cheese pull.

Note: If you have some dried herbs like thyme or oregano in your pantry, add a teaspoon to the tuna mixture. They work really well with the tomato and onion.

Storage Instructions

This tuna casserole keeps well if you have leftovers. Here’s how to store it properly:

Refrigerating Leftovers

Let the casserole cool completely before storing. Cover the casserole dish with plastic wrap or transfer portions to airtight containers. It will keep well in the refrigerator for 3-4 days.

To reheat, microwave individual portions for 1-2 minutes until heated through. For larger amounts, reheat in the oven at 350°F for about 15-20 minutes.

Freezing Instructions

This casserole freezes really well. You can freeze it either before or after baking:

Before baking: Assemble the casserole, but don’t bake it. Cover tightly with plastic wrap and then aluminum foil. Freeze for up to 3 months. Thaw overnight in the refrigerator before baking. Add 15-20 minutes to the baking time.

After baking: Let it cool completely, then portion it into freezer-safe containers. Freeze for up to 2 months. Thaw in the refrigerator overnight and reheat in the microwave or oven until hot.

Top Tip: For best results when freezing, leave the cheese topping off and add fresh cheese when reheating. This prevents the cheese from becoming rubbery after freezing and reheating.

More Potato Recipes to Try

If you’re looking for more quick dinner ideas that turn simple potatoes into something comforting and delicious, you’ll love these easy recipes:

• CRISPY Canned Tuna and Potato Patties – These tuna and potato patties are quick, budget-friendly, and so tasty. Crispy outside, soft and flavorful inside—perfect for using up leftover potatoes and making a protein-packed dinner in no time.
• Crispy Potato Cheese Balls with a Gooey Center — A fun and affordable way to use up leftover potatoes. These crispy bites are quick to make and packed with cheesy goodness — great for a snack or an easy side dish for dinner.
• The Crispiest Air Fryer Baked Potatoes — A fast, hands-off way to get perfectly crispy baked potatoes with fluffy insides. Ideal for busy nights when you want a comforting side with minimal effort.