Keto Tuna Noodle Casserole with Zoodles and Cheese Sauce

June 7, 2025

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This keto tuna noodle casserole is a low-carb take on the classic. Spiralized zucchini stands in for egg noodles, and a homemade cheddar and Parmesan cream sauce replaces the canned soup. It is creamy, cheesy, and full of comfort.

Everything cooks in one skillet on the stove, so dinner is ready in about 30 minutes. It uses canned tuna and a few fridge staples, which makes it an easy weeknight meal.

Why This Keto Tuna Noodle Casserole Works

Zoodles keep it low carb. Zucchini noodles have a fraction of the carbs of pasta and soak up the sauce well.
Real cheese sauce. Heavy cream, sharp cheddar, and Parmesan make a rich sauce with no flour or canned soup.
Dry-cooking the zucchini. A quick toss in a dry skillet pulls out water so the sauce stays thick.
Pantry protein. Two cans of tuna add plenty of protein for very little cost.

Ingredients and Easy Swaps

You need 3 medium zucchini, spiralized, or a package of store-bought zoodles. The sauce uses 2 tablespoons of butter, 2 cloves of garlic, 1 cup of heavy cream, 1.5 cups of shredded sharp cheddar, and a quarter cup of grated Parmesan. Season with salt, black pepper, and half a teaspoon of dried parsley or Italian seasoning if you like. Add two 5 ounce cans of tuna, drained and flaked.

Tuna: Tuna packed in water or oil both work. Canned salmon or shredded chicken also work.
Zucchini: Yellow squash noodles or hearts of palm noodles are other low-carb options.
Cheese: Colby Jack or Gruyère melt well. Pre-shredded cheese has anti-caking powder, so block cheese gives a smoother sauce.
Add-ins: Peas are classic in tuna casserole but add carbs. Chopped spinach or mushrooms are lower-carb picks.

How to Make It at a Glance

Cook the zoodles in a dry skillet for 3 to 4 minutes, then drain them in a colander.
Melt the butter in the same skillet and cook the garlic for 1 minute.
Add the cream and bring it to a gentle simmer.
Stir in the cheddar, Parmesan, salt, pepper, and herbs until smooth.
Add the tuna and zoodles, toss to coat, and simmer 2 to 3 minutes until hot.

The full recipe card is below. For a baked, bubbly top like a classic casserole, move it to an oven-safe dish, sprinkle with a little extra cheddar, and broil for 2 to 3 minutes. Watch it closely so the cheese browns but does not burn.

Common Mistakes to Avoid

Overcooking the zoodles. They release water and turn mushy. Just warm them through.
Skipping the drain. Let the zoodles sit in a colander while you make the sauce, and pat them dry if they look wet.
Boiling the sauce. High heat can make the cheese turn grainy or oily. Keep it at a gentle simmer and add cheese a handful at a time.
Wet tuna. Drain the tuna well, pressing out the liquid with a fork.

Variations

Crunchy topping: Sprinkle crushed pork rinds mixed with Parmesan on top and broil until golden.
Tuna melt style: Add a spoon of Dijon mustard and a squeeze of lemon to the sauce.
Spicy: Add red pepper flakes or a dash of hot sauce.
Not low carb: Use 8 ounces of cooked egg noodles in place of the zucchini.

What to Serve With It

A simple green salad with a lemon vinaigrette cuts the richness. Roasted broccoli, steamed green beans, or garlicky sautéed spinach also pair well. For anyone not eating keto, a slice of crusty bread on the side is nice for the sauce.

Storage and Reheating

This dish is best fresh, since zucchini releases water as it sits. Store leftovers in a covered container in the fridge for up to 2 days. Reheat gently in a skillet over low heat or in the microwave at half power, stirring often. Heat it to 165°F. A splash of cream helps loosen the sauce. Freezing is not recommended because the zoodles turn soft and watery.

How to Make Zucchini Noodles

A handheld or countertop spiralizer is the easiest tool. Trim both ends of the zucchini, then twist or crank it through the blade. If you do not have one, use a vegetable peeler to make long, wide ribbons, or a julienne peeler for thin strands. Cut very long noodles in half with kitchen scissors so they are easier to eat. Three medium zucchini make about 6 cups of raw zoodles, which cook down a lot.

Keto Tuna Casserole FAQ

Why is my sauce watery?
The zucchini released extra water. Next time, cook them a minute longer in the dry pan and drain them well. Simmer the finished dish a few more minutes to thicken.

Do I need to cook the tuna?
No. Canned tuna is already cooked. It just needs to warm through in the sauce.

Is this dish really keto?
Yes. Zucchini, cream, cheese, and tuna are all low in carbs. Most of the carbs come from the zucchini and a little from the cream. Skip peas and other starchy add-ins to keep it strict.

Can I make it ahead?
Make the cheese sauce up to a day ahead and keep it in the fridge. Cook the zoodles fresh, then warm the sauce and toss it all together right before serving.

Can I use half and half?
Heavy cream works best. Half and half is thinner and more likely to separate, and it has more carbs.