This low carb keto tuna casserole is made extra delicious with tender cauliflower, fresh zucchini, a creamy herb sauce, chunky tuna, and layered with ooey gooey melted cheese. Sure to become a new family favorite - this healthy casserole is a high protein, gluten free, sugar free, keto-friendly dinner idea! It can also be made low fat and lighter with easy substitutions.
Why You'll Love This Keto Tuna Casserole
Inexpensive. Using canned tuna makes for a very cost-effective meal! Also, because it is a pantry staple, it has a long shelf life and doesn't take up precious space in your fridge or freezer.
Delicious. The combination of tuna, dill, sauce, zucchini, and cheese make this a very delicious keto tuna casserole. The zucchini and cauliflower give it a fresh taste that balances the melted cheese and tuna.
Healthy. You'll love this healthy tuna casserole - it's high in protein, gluten-free, low carb, keto, and has no added sugar. Oh, and it's a great way to sneak in extra veggies! Between the cauliflower and zucchini, you have a full serving of vegetables in this recipe!
If not following keto, lower the fat by using a low-fat or fat-free sour cream and mayonnaise. Reduce the cheese to 1 cup.
Low Carb Tuna Casserole Ingredients
Here are the ingredients that you will need to make this casserole recipe:
- Cooked Cauliflower - microwave, steamed, boiled, or roasted cauliflower (oven or air fryer) all work perfectly.
- Canned Tuna - you can also use shrimp, crab, or salmon.
- Celery
- Green Onions - finely chopped shallots or red onion can be used in place of green onion.
- Mayonnaise - use any favorite brand. It's fine to use a lower-fat variety if needed.
- Sour Cream - same as the mayo, use a lower fat if needed.
- Dijon Mustard
- Fresh Dill - chives, basil, parsley, and thyme can also be used.
- Kosher Salt - add according to the recipe and adjust after serving.
- Ground Black Pepper
- Zucchini
- Shredded Jack or Cheddar Cheese - mozzarella, swiss, or gouda will work fine too.
- Crushed Ground Pork Rinds - you can crush your own pork rinds or buy them already crushed.
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Tuna Casserole Keto and Low Carb Variations
- Make this a keto seafood casserole - most canned seafood can replace the tuna - salmon, crab, and shrimp. A combination is also delicious.
- Use a salted seafood seasoning in place of the salt. Adjust seasoning to taste with salt after serving.
- Slice the zucchini or make zucchini noodles. I found it faster to slice then to make the zucchini noodles.
- ¼ cup softened cream cheese can be added if desired.
- Process keto bread in a food processor and use as breadcrumbs instead of pork panko.
- Use a full fat, low fat, or fat free mayonnaise and sour cream - depending upon your dietary needs.
- Add a little spice with some red pepper flakes or cayenne pepper.
- Substitute broccoli for cauliflower.
How To Make Keto Tuna Casserole
Okay, this is so easy and good you will wonder why you have never made this before! 🙂
Prep And Assemble Your Ingredients
Cook the cauliflower. Preheat your oven to 350 degrees. Drain the tuna and set aside. Chop your vegetables and assemble all other ingredients.
Make Tuna Mixture
In a bowl, combine cauliflower, drained tuna, celery, green onions, mayonnaise, sour cream, mustard, herbs, salt, and pepper.
Layer Zucchini and Cheese
In a buttered 1.5-quart baking dish, spoon half of the tuna and sauce mixture and spread evenly. Layer with half the zucchini and then half the cheese.
Top with the remaining half of the tuna, zucchini, and finish by topping with cheese.
Sprinkle top with pork rind panko.
Bake
Bake for 40 minutes or until the dish is hot and the cheese is bubbly.
Let the casserole sit for about 5-10 minutes before serving.
How To Serve Low Carb Keto Tuna Casserole
Garnish with fresh herbs.
- Topping it with diced tomato and sometimes avocado is a great way to sneak in extra veggies!
- Top it with a dollop of sour cream or additional shredded cheddar cheese, jack or parmesan cheese.
- Meal idea! Serve your tuna casserole with a fresh green salad and this delicious Creamy Dill Dressing.
Top Tips
- Slice the zucchini very thin to help it cook faster in the casserole.
- Adjust any seasoning to taste.
- Use 1 teaspoon dried herbs for every 1 tablespoon.
- If the casserole is browning too fast, cover it with foil.
- Crush your own pork rinds if you can't find the panko.
- Use butter, olive oil, or cooking spray to coat the casserole dish.
FAQs
Yes! Tuna is very low in carbs and is perfect on a low-carb and keto diet. It is also sugar-free and gluten-free.
The answer to that depends on which recipe you are following and can vary widely. This tuna casserole contains 4.8 grams of cabs, 1.4 g of fiber, and only 3.4 grams of net carbs.
Yes, absolutely. Tuna has almost no carbs, sugar, and is gluten-free. Because it is lower in fat it is usually combined with healthy fats such as avocado, mayonnaise, cheese, etc.
To store leftovers, let the casserole cool completely, then transfer to an airtight container. Store in the refrigerator for up to 4 days. See reheating instructions below.
Oven: preheat oven to 350 degrees. Transfer the casserole to an oven-safe dish and cover it with foil. Bake until heated through, about 20 minutes.
Microwave: in a microwave-safe dish, cook covered for 1 to 2 minutes until heated through. Adjust heating time and temperature according to your microwave wattage.
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📖 The recipe.
Low Carb Keto Tuna Casserole Recipe
Ingredients
- 3 cups cooked cauliflower (florets about 1" to 1½" in size)
- 2 (6.5-ounce) cans drained tuna (or, salmon, crab, or shrimp)
- ½ cup chopped celery
- ½ cup sliced green onions
- ½ cup mayonnaise
- ½ cup sour cream
- 2 teaspoons dijon mustard
- 1 tablespoon fresh dill (or, 1 teaspoon dried)
- ½ teaspoon kosher salt
- ¼ teaspoon pepper
- 1 small zucchini (very thinly sliced)
- 1½ cups shredded cheddar or jack cheese (or, mozzarella, swiss, gouda)
- ¼ cup crushed pork rinds
Instructions
- Preheat oven to 350 degrees. Prep and assemble your ingredients. Drain tuna (or other seafood), and set aside.
- In a bowl, combine cauliflower, tuna, celery, green onions, mayonnaise, sour cream, mustard, dill, salt, and pepper.
- In a buttered 1½-quart casserole dish, spoon half of the tuna mixture. Layer half the zucchini and half the cheese. Top with the remaining half of the tuna mixture and zucchini. Finish with cheese.
- Sprinkle crushed pork rinds over the top. Bake at 350 degrees for 40 minutes until the dish is hot and cheese is bubbly.
- Sprinkle with fresh dill and serve.
Video
Kori's Tips
- Don't miss all of our helpful hints, substitution ideas, cooking tips, and other delicious recipes that can be found in our post. Check it out!
- VARIATIONS: Substitute canned shrimp or salmon; use chives, parsley, or thyme in place of dill - or a mix; mozzarella, jack, or cheddar cheese can be used; green onion can be added to the casserole.
- TIPS: Roasted (oven or air fryer), boiled, or steamed cauliflower will all work great. The best flavor is roasted cauliflower. Reduce the amount of salt called for when roasting.
- SERVING SUGGESTIONS: Adjust salt and pepper. Garnish with fresh dill or chives and diced tomato.
Nutrition
© 2025 Seeking Good Eats™
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Lori
I made this and used a 1/4 cup Boursin cheese and 1/4 cup mayonnaise instead of the full 1/2 cup of mayo. I didn’t have zucchini so I used peas instead. Turned out great! I also roasted the cauliflower. Will make again.
seekinggoodeats
Thank you! That sounds fabulous and I'm totally going to try your idea. thanks for sharing! 🙂
Heather Rasmussen
Tried this recipe tonight.. it was delicious!
seekinggoodeats
Thank you! 🙂
Harvey
I modified this recipe a lot for what I had on hand, but I really liked it as a basis for a non-pasta tuna casserole. Made it with cream of mushroom soup, broccoli instead of cauliflower, and mixed veggies instead of zucchini. Still very tasty! Will make again!
Kori
Sounds delicious and thank you! 🙂
Bobs Mom
You give the nutritional values per serving which is great but nowhere did I see how many servings this made! Can you leave it in the reply? Thanks
seekinggoodeats
Hello! 6 servings 🙂 Enjoy! I love this casserole in fact I added it to my menu this week! LOL!