Keto tuna casserole

Keto tuna casserole

Just like mom used to make—NOT. Ditch the noodles in favor of celery, onions, and peppers, and indulge in a keto meal that's ready in 30 minutes. It's a whole new, delicious thing.

Keto tuna casserole

Just like mom used to make—NOT. Ditch the noodles in favor of celery, onions, and peppers, and indulge in a keto meal that's ready in 30 minutes. It's a whole new, delicious thing.
4 servingservings


  • 2 oz. 50 g butter
  • 1 1 yellow onionyellow onions
  • 1 1 green bell peppergreen bell peppers
  • 513 oz. 150 g celery stalkcelery stalks
  • 16 oz. 450 g tuna in olive oil, drained
  • 1 cup 225 ml mayonnaise
  • 4 oz. 110 g freshly shredded parmesan cheese
  • 1 tsp 1 tsp chili flakes
  • salt and pepper
  • 6 oz. 175 g baby spinach
  • 4 tbsp 4 tbsp olive oil


Instructions are for 4 servings. Please modify as needed.

  1. Preheat the oven to 400°F (200°C). Chop onion, bell pepper and celery finely and fry in butter in a large frying pan until slightly soft. Season with salt and pepper.
  2. Mix tuna, mayonnaise, parmesan cheese and chili flakes in a greased baking dish. Add fried vegetables and stir.
  3. Bake for 15-20 minutes or until golden brown.
  4. Serve with baby spinach and olive oil.


Canned tuna is a life-saver when fridge and freezer are empty. Try to choose high-quality, MSC-labeled tunafish—preferably in olive oil instead of sunflower oil.

You might also like

A little sneak peek...

With Diet Doctor Plus you get access to tons of keto meal plans, including dairy-free and vegetarian versions, meal plans adapted for intermittent fasting, quick-and-easy and budget keto meal plans. Below, see our latest one.

Low carb: Vibrant colors

This vibrant and flavorful meal plan celebrates color! Enjoy a week with some of our most colorful recipes. Bring your taste buds alive via the power of vision. There will be no need to remind yourself to eat your greens this week!

Full meal plan →

Get the full Diet Doctor experience for free

With Diet Doctor Plus, you get instant access to all of our delicious recipes, popular meal plans, meal planner tool, inspiring videos and educational guides. As a paying member you also help us in our mission to empower even more people. What are you waiting for? Sign up today and try for free for a month. Cancel anytime you want.
1 2


  1. Chad
    Very filling and the tuna was a welcome change from all the yard-bird I've been eating lately. This was very quick and supper simple to fix. I did omit the green bell pepper and chili flakes I love them both but not sure I would use them with tuna. I did sprinkle the top with bacon bits and a thin layer of a fiesta cheese mix before putting it in the oven. I might add some green peas, mushrooms and pimentos next time although will bump up the carbs a bit.
  2. suzann
    Do you foodies think i could sub salmon? I'm new to sea food but I've got some salmon in the freezer.
  3. Carole
    This is pretty good, not exciting, but I'll make it again. I followed the recipe pretty closely. The parmesan gets some crunchy bits in the oven, which is great. I used tinned tuna, but you could also use tinned salmon.
  4. Maha
    I made this last night, and holy tuna casserole, was this delicious! I followed the recipe nearly exactly (yellow bell pepper instead of green, less chili flakes to taste). My kids loved it too, even my pickier eater. My other son wanted to make sure there were leftovers for his lunch today. And I'm looking forward to lunch too! This is a great recipe to double or triple and freeze in portions. I think the key to this recipe is to use quality ingredients. The mayonnaise I bought is a small fortune, but it's made with normal ingredients (except the soybean oil) and tastes really good. The tuna I use is not the yucky standard that is cooked twice, but one that is cooked just once and retains all the yumminess of tuna. I think this recipe lends itself well to variations - adding mushrooms, using jalapenos, making lettuce boats/bites, topping a tomato bowl or slice and add chopped avocado, etc. An excellent recipe, thank you!
  5. Cindy
    Very good! I used chopped up broccoli stems since I didn't have a pepper on hand. Also added mushrooms and cheddar cheese on top. I'll be making this again!
  6. carol
    Just made this, with grated mozzarella and grated cheddar on top. Lovely.
  7. Unni Furseth
    One of my favorites! I'm just about to make 12 portions and freeze, so I have something delicious the days I don't have the time to cook. And you get first class mayonnaise by making it yourself, recipe on this fantastic website! Thank you for all these wonderful, tasty keto recipes!!!
  8. Ibán
    very tasty thanks!
    however mine came out with a lot of oil on the bottom of the pan, maybe because I used olive oil based mayonnaise
  9. Rads
    Hi! This looks delicious. I live in India and ovens are not staple here, just stove tops hobs. Can I make this on stove top? If yes, how long should the mix cook? Or is it better to make this in an electronic slow cooker, which I have?
  10. Rads
    And can I use fresh tuna chunks, which I just froze today!
  11. Karina
    Loved it!
  12. Brenda
    Does this really take 4 4oz cans of tuna to make the 1 pound?
    Reply: #14
  13. Phil
    Perhaps my mayo in the UK is different but the amount of oil when I took it out of the dish was incredible and swamped the plate ... I followed the recipe exactly? Any ideas? or maybe I can replace the mayo with something else?
  14. Hlhabq
    I had the same question when u saw the amount of things cheese in the recipe.
    Reply: #15
  15. Hildyhorse
    ... amount of TUNA...
  16. 1 comment removed
  17. Jared
    To be honest: I was surprised this was good as it was. Made no substitutions, followed directions exactly and it was a win. If you ever had a subway tuna sandwich that was toasted to be warm, it's just like that.
  18. Carrie
    I had major reservations about this recipe mainly due to the all mayo base, but this turned out great! I used a 7 oz can of tuna in water instead of oil. And also added shredded cheese on top. I think I could double the tuna next time and sub some different veggies...definitely satisfied my comfort food craving while trying to stick to low carb!
  19. 1 comment removed
  20. Matt
    Are these nutrition facts per serving? Thanks
    Reply: #21
  21. Peter Biörck Team Diet Doctor
    Hi Matt!

    Yes. :)

    Are these nutrition facts per serving? Thanks

  22. Nicoleta
    It was the first time I tried baking mayo and I have to say I'm not a huge fan of the process. The recipe sounds great but, as you'd expect, most of the oil separates from the egg yolk during baking and you're left with and incredibly oily warm tuna salad with sauteed vegetables. Still, it was a good attempt at innovation.
    Reply: #48
  23. Christy
    The mayo in this recipe was really disgusting to me -- oil everywhere. I'm going to search for another recipe for tuna casserole or figure out some way to modify this. Sour cream, maybe?
    Replies: #39, #49
  24. Jill
    I made this last night to keep for dinner throughout the week. I am pleasantly surprised at how good this turned out. Like someone else, I also used canned tuna in water and drained it. I used 3 cans and kind of eye balled the rest of ingredients. I also added two cloves of garlic and topped mine with shredded mozzarella because I’m a cheese addict. Came out so good. It’s definitly a refreshing recipe from all the red meat and chicken I’ve been eating. I lost 20lbs following recipes and advice from this site, such a great resource!
  25. Gloria
    i wasnt sure how this would turn out, but it was the quickest, easiest, most delicious meal i've made. everything complimented everything perfectly ! love it, defs one of my faves 😊😊
  26. Rosemary
    Did not this at all. I agree with Christy. Oil everywhere. Too greasy. Hardly any taste to it.
  27. Michelle
    Could you use sour cream instead of mayonnaise?
  28. Cindy
    can someone help me please! I'm confused I put for one person and when I open the recipe it says four servings. Does that mean I can have up to four servings? lol sorry if it sound silly.
    Reply: #30
  29. Jacqueline
    This is the most delicious thing I have eaten in my entire life!
  30. Jacqueline
    You can alter the recipe for one serving and it gives you the calorie, carb, fat breakdown down below
  31. Nicole
    Absolutely delicious! I topped with mozzarella cheese and love the chilli flakes.
  32. Brenda
    Hi all , tuna makes me repeat can I use the canned chicken instead ? Thank
    Brenda PM ( since the is more than 1 Brenda 😀
  33. Margot Campos
    I really wanted to like this dish but found myself disappointed. It was way too oily and I didn’t like the taste.
  34. Katheryn
    I agree with Margot. It was too salty and heavy and I didn't like it all. Fortunately, my husband loved it so he can finish it off.
  35. Dorothy
    Yum! Very, very tasty indeed. I only had supermarket mayo to hand and substituted mushroom for pepper. Will definitely make again, thank you!
  36. Jacolyn
    I made this tonight for dinner and I liked it! Loved the hint of the hot peppers. I actually added spinach to it instead of on the side. I will make this gain. Very filing too!
  37. Lucy
    Can I use canned tuna in water or does it have to be in olive oil? Also can I sub out parm cheese for regular cheese?
    Reply: #38
  38. Kristin Parker Team Diet Doctor

    Can I use canned tuna in water or does it have to be in olive oil? Also can I sub out parm cheese for regular cheese?

    You can use either tuna you prefer. For the cheese, if you make a sub, it can affect texture and taste as other cheeses don't behave the same in baking as parmesan. You can experiment to see if it works for you though.

  39. Julia Britt
    Agreed. I added a bit of turmeric and cayenne because it didn't look appetizing to me. It is waaaay too rich. It needs noodles to make it worth eating more than one bite, but then its not or to friendly. Never again!
  40. Sherri S.
    I purchase the BIG cans of water-packed tuna at Sam's Club or Gordon Foods as you get a LOT more tuna and less juice than when you try to use the smaller cans, perfect for preparing family-sized meals and you aren't opening 8-12 smaller cans of mostly juice. The price is reasonable, too, when buying tuna like that. You get large chunks of tuna as opposed to fine shreds. I keep a few small cans around if I want to prepare a small amount for my lunches, but always have a large can for casseroles in the pantry.
  41. Emma
    I'll be honest I didn't hold out much hope for this recipe; it just seemed too simple. However it was incredibly tasty, looking forward to my dinner tomorrow now!!!
  42. Erica
    I made this recipe last night. It was very oily and creamy. I used my keto Mayo and felt it may have been better with sour cream. However, it had a delicious taste. I might try the recipe again with a few modifications.
  43. Johnda
    1 pound is equal to 16 ounces. 4x4 is 16.
  44. Elisabeth
    This was very tasty and will quickly be one of my favourites. Thanks to everyone who contributes to the recipes...makes life so much easier
  45. Mieka
    I've never eaten tuna casserole in my entire life. Looks like I'm about to try it. :-)
  46. Dianna
    Very tasty! I used Avocado mayonnaise and it wasn’t too greasy but I did top with a mixture of cheddar and jack cheese
  47. 1 comment removed
  48. The Ghost Critic
    Oil doesn’t separate if you did it right
  49. The Ghost Critic
    No sour cream, just follow directions 😈
  50. Paulina
    Can I freeze
    Reply: #51
1 2

Leave a reply

Reply to comment #0 by