- Liv Banks
- Created: March 18, 2025
- Updated: October 24, 2025
Ever had one of those days when you’re staring into the fridge, trying to piece together a meal? I’ve been there too. Just last week, I’d used up all my chicken breasts for a keto casserole with broccoli, and there was nothing thawed or defrosted. My inner voice was screaming, “What now?” That’s when I remembered my trusty pantry staple: canned tuna.
With a few veggies in the fridge and some basic keto-friendly ingredients, I threw together this keto tuna casserole. It’s creamy, cheesy, and packed with flavor. Plus, I love it when I whip up something so quick and easy, and my husband goes, “Oh, this looks like a lot of effort.” I just nod my head in agreement. hehe
And I really hope you have some fresh or even dried dill on hand because fish and dill are a match made in heaven. But, if you don’t, any dry herb will do.
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Why You’ll Love This Recipe
This dish has all the good old classic flavors of a traditional tuna casserole but with a low-carb twist. It’s perfect for anyone following a keto diet or looking for an easy low-carb recipe to whip up after a long day.
Here’s why it’s a keeper:
Low-carb comfort food: Packed with healthy fats, protein, and veggies, but it’s super filling and satisfying.
Customizable: Don’t have cauliflower? Use cabbage or zucchini noodles instead. Prefer mozzarella cheese? Go ahead!
Meal prep-friendly: Make it ahead and enjoy it throughout the week.
Simple ingredients: No need for anything fancy—just pantry staples, fresh veggies and a generous amount of cream and cheese (best part about keto, right?!).
Ingredients You Will Need For This Keto Tuna Casserole
Substitution Tip
I didn’t have any cream cheese on hand once, so I decided to use sour cream instead of cream cheese and cream. I used 1 and 1/2 cups of sour cream and it worked really well too. Sour cream and tuna goes well together. So if you prefer to use sour cream instead of cream cheese and cream, you totally can.
Also, I didn’t have any green peas, so instead I finely chopped some asparagus, and it was great too. So, pretty much, you can add almost any veggies you want to use up in the fridge that need to be cooked ASAP. And that is one of the best parts of this keto tuna casserole with veggies.
Olive Oil
As always, I forgot to take a photo of the olive oil I used to sauté vegetables with, so I’ll add that in. I used 1/4 cup. Sorry, it’s one of those items that sits next to my stove top, and I forget all about it when I flip my camera out.
Tips for the Best Keto Tuna Casserole
- Chop the cauliflower into small florettes and chop up the stems of the cauliflower. Smaller pieces will mix better together with the rest of the ingredients, cook faster, and you will get a bit of everything in each bite when eating it.
- Sauté the vegetables in the 1/4 cup of olive oil, or if you are using the oil from the canned tuna, you can use that instead.
- Begin with sauteing onions, give them about 5 minutes to become soft and golden, then start adding other vegetables except fresh herbs. Sauté till soft, tender and golden and until the moisture is cooked out.
- Mix the sauce ingredients in a large bowl, to which you will add all the rest of the ingredients later, so make sure it’s a big bowl.
- Save about a 1/3 of each cheddar and parmesan to use for topping before baking the keto casserole.
- Once the sauce is mixed well, you can transfer your sauteed veggies into this bowl, if it’s still warm, even better, as it will help melt the cheeses and meld together.
- Flake the tuna in the can with a fork to break it up, and add it to the veggie and sauce mixture. Mix everything well, until all the ingredients are covered in sauce and well combined.
Let’s Chat About Tuna for a Sec
Tuna is one of those ingredients that works beautifully in low-carb recipes like this one. Here’s why it’s such a great choice:
High Protein & Low Carbs
Tuna is naturally high in protein and contains virtually no carbs—perfect for anyone following a low-carb keto lifestyle.
Rich in Nutrients
It’s loaded with B vitamins (for energy), selenium (an antioxidant), potassium (for heart health), and omega-3 fatty acids that support brain function.
Selecting the Best Tuna
When choosing tuna for your keto casserole, keep these tips in mind:
Types of Tuna
Skipjack or light tuna: Lower in mercury, making it a safer choice for regular consumption.
Solid white albacore tuna: Richer flavor but higher in mercury; enjoy occasionally.
Sustainability
Look for labels indicating “sustainably caught” or “pole-caught.” The Marine Stewardship Council (MSC) stamp is a good indicator of sustainable fishing practices.
Tuna Packing Options
Water-packed: Lower in calories, ideal for weight management.
Oil-packed: More flavorful, but higher in calories.
But What About the Mercury in Tuna?
Mercury in tuna is a valid concern, but you can minimize risks:
Choose lower-mercury options: Opt for skipjack or light tuna over albacore or yellowfin.
Limit consumption: Follow FDA guidelines for tuna intake based on your age and health status.
Diversify your fish intake: Include other low-mercury fish like salmon, sardines, or mackerel in your diet.
Check for “tested for mercury” labels on packaging.
Remember, the benefits of consuming tuna as part of a balanced diet typically outweigh the risks for most people.
Keto Tuna Casserole Recipe
Equipment
Ingredients
Main ingredients
- 1 large can 15 oz / 450g can tuna in olive oil
- save the oil for cooking the vegetables
- 1 head cauliflower (you can use frozen cauliflower too, but thaw out and drain well before cooking)
- 1/4 cup peas or a bunch of asparagus spears
- 1/2 cup chopped red peppers/capsicum
- 1/2 cup carrot, finely diced or shredded
- 1 medium size white/yellow onion
- 1/2 cup freshly copped dill or any herb of your choice
- 1 tsp Salt
- 1/2 tsp black or white pepper
For the sauce:
- 2 tbsp fresh dill, chopped (or 2 tsp dried)
- 1 cup 250g of full fat sour cream or heavy cream sour cream is better, but cream will work too
- 1/2 cup cooking cream cheese or regular cream cheese, softened
- 1/2 cup parmesan cheese, grated
- 1 cup cheddar cheese, shredded
Instructions
Oven Method
- Preheat your oven to 355°F (180°C).
- Chop cauliflower into small florettes and make sure to chop the stems/legs of each florette finely, to avoid large chuncks of cauliflower.
- Chop all the other vegetables finely and grate the carrot on a grater.
- Heat up the olive oil from tuna can in a large sauteing pan.
- Saute onions for 5 minutes or until they are soft and slightly golden.
- Add salt and pepper to the onions while they are still cooking.
- Add other vegetables and saute till everything is soft and the water is cooked out.
- Chop the dill and set a little bit aside, for garnishing later.
- In a large bowl, mix the cheeses and creams with chopped dill, leaving about 1/3 of each cheese for topping later.
- Once the sauce is ready, add the sauteed vegetables to the sauce.
- Flake the tuna apart with fork, and add it into the vegetable and sause mix, combine everything well.
- Transfer to the 9 x 9 or similar size baking tray and sprinkle the remaining cheese on top evenly.
- Bake for about 20-25 minutes until the top is golden brown.
- Sprinkle with extra fresh dill before serving.
- Store leftovers in the baking tray covered with plastic wrap after it's completely cool.
Pressure Cooker Method
- Follow steps 2-8 from the above instructions in your pressure cooker pot. Do not add the cheeses to the pot before cooking, as they might burn. Instead, add the tuna right to the vegetables.
- Close the lid and cook on high pressure for 3 minutes.
- Quick-release the pressure and stir in the sauce, allow it to melt in the pressure cooker for a bit, before serving.
Slow Cooker Method
- Mix all ingredients except the sauce in your slow cooker.
- Cook on low for 3–4 hours.
- Add cheddar cheese during the last 30 minutes of cooking.
Notes
Nutrition
Tips for Success
Remove excess water: Pat your tuna dry with paper towels to avoid watery casserole sauce.
Extra veggies: Add green beans or green peppers if you have them on hand.
For picky eaters: Blend some of the veggies into the sauce mixture so they’re hidden but still nutritious.
Variations: Different Ways to Customize
This keto tuna casserole is versatile! Here are some ideas:
Swap cauliflower rice for shirataki noodles or zucchini noodles.
Add cream cheese or sour cream for an ultra-creamy texture.
Try mozzarella cheese instead of cheddar.
Use chicken broth instead of heavy cream if you prefer a lighter sauce.
Storage & Meal Prep
This healthy tuna casserole is ideal for meal prep:
Store leftovers in an airtight container in the fridge for up to 3 days. I love my Pyrex Glass Baking Dish as I can bake in it and it comes with air tight lid which means I don’t have to move my casserole into another dish for refrigeration.
Reheat in the oven or microwave until heated throug
If you’re prepping ahead of time, assemble everything except the cheese topping and store it in your baking dish until ready to cook.
You Might Also Like These Similar Recipes...
This keto tuna casserole is more than just an easy recipe—it’s part of a long list of keto comfort foods that make sticking to your low-carb diet enjoyable. It has all the good old classic flavors without any extra carbs from egg noodles or bread crumbs.
For me, it brings back childhood memories of cheesy casseroles my family made growing up—though this version skips potato chips on top! Whether you’re cooking for yourself or feeding picky eaters at home, this dish checks all the boxes: simple ingredients, creamy texture, and plenty of flavor.
So next time you’re craving something hearty but keto-friendly, give this great recipe a try! It might just become your favorite recipe for busy weeknights.
Happy cooking!
3 Responses
Absolute hit. Thanks so much and it was so easy to make. Will definitely be making it again. Many thanks 🙏🏻
So glad you like it, thank you for the comment.
Glad you like it. 😊