Looking for a fresh twist on the classic tuna mayo onigiri with an authentic Japanese taste? This version features creamy avocado, melty cheese, and Kimono Mom's Umami Sauce®—an additive-free blend of savory Japanese ingredients. With a filling that’s both indulgent and satisfying, it’s sure to become your new favorite.
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If you've ever visited Japan, you've definitely seen tuna mayo onigiri in convenience stores—they're everywhere!
When I first came to Japan in the early 2000s, I'm pretty sure tuna mayo was the first onigiri I tried. Or maybe it was grilled salmon onigiri—my American taste buds were still adjusting! Back then, fillings like simmered konbu or mentaiko seemed foreign, and little did I know how much I'd come to love them.
Before moving to Japan, I didn’t even know what an onigiri was. I had forgotten just how satisfying tuna and mayo could be—until now. This recipe brought me back to those childhood tuna melts my sister and I would make in the toaster, long before I even knew what umami meant.
If you’re loyal to your traditional tuna mayo onigiri, I totally get it—why fix something that isn’t broken? But I truly believe this recipe will change the way you see this convenience store classic. My tuna mixture, made with Kimono Mom's Umami Sauce and paired with creamy avocado and melty cheese, is a twist that took me months to perfect. The result? An irresistible combination that’s both indulgent and satisfying. The effort was well worth it!
Why You’ll Love This Tuna Mayo Onigiri Recipe
Once you try these new tuna mayo onigiri, you'll be hooked—line and sinker.
All you need to make them is one secret Japanese ingredient (available at Whole Foods), some decent-quality Japanese rice, and nori seaweed.
The rest of the ingredients you can find at any grocery store—no need for special trips to an Asian market or exotic specialty store. And honestly, it doesn’t get much simpler than a can of tuna.
Even with such simple, everyday ingredients, these creamy-filled onigiri are incredibly satisfying. When done right, tuna mayo is the ultimate onigiri filling.
If it weren't for the mercury in large ocean fish like tuna and concerns about sustainable fishing, I could live on these every day. Seriously.
But fair warning: these onigiri are so good, they're addicting.
If you need any help making my tuna rice balls with avocado and cheese, just leave me a comment below! I personally respond to every message.
❤️ & 🍙 from Japan, Matt
PS. A special thank you to Moe "Kimono Mom" for the inspiration to create this recipe and for teaching me how to make perfect rice in her donabe!
Recipe at a Glance
Cuisine— Japanese Course— Breakfast, Lunch, Dinner, or Snack Dietary Info— Pescatarian, Gluten-free Skill Level— Medium (requires some practice for novice cooks)
Tuna Mayo Onigiri Ingredients
Basic onigiri ingredients:
Japanese white rice: It's important that you use short-grain rice. It's sometimes labeled "sushi rice" outside of Japan. In my easy onigiri recipe post, I go into detail about what rice I use. You'll also find my list of recommended brands.
Cold water: The quality of water you use to cook rice matters. Always use clean, filtered water whenever possible for the best results. Cold water is preferable, as it helps the rice absorb moisture evenly during cooking, but room-temperature water will also work just fine.
Nori sheet: Outside of Japan, it can be difficult to find higher-quality nori. Exported, premium-quality nori can be pricey but you can taste the difference. You can buy full-size nori sheets and cut them into ⅓-sized strips. Or buy nori seaweed strips that are already the perfect size for wrapping onigiri.
Salt: I prefer to use sea salt that's fine grain, not coarse salt. If I only have my go-to coarse salt on hand, I grind it down with a mortar and pestle or even a spoon if I'm being lazy.
Onigiri Filling (& Topping) Ingredients
Canned Tuna: I made this recipe with a regular-sized can of tuna (oil-packed). You could try water-packed tuna for a lighter taste. With the added mayo and umami sauce, I don't think it really matters. My only recommendation is for line-caught, high-quality tuna that's not overfished.
Avocado: It's best to use an avocado that's not overripe. You don't want it to be too soft or mushy. When you press your thumb against the bottom, it should only dent in slightly to gentle pressure. And if you check underneath the stem, you want it to be a light green color.
Mayonnaise: I use a Japanese mayonnaise that's a bit healthier than Kewpie mayo. It doesn't contain additives. Outside of Japan, you can find Kewpie mayonnaise. The good thing about Kewpie is that it doesn't contain added sugar. I recommend using Japanese mayonnaise if you can find it. You can also make homemade Japanese (Kewpie) mayonnaise.
Umami Sauce: I used Kimono Mom's "Umami Sauce", which is now available at Whole Foods across the USA! Alternatively, you could use tsuyu or soy sauce, in smaller amounts, if you don't live in North America or Japan. To make your onigiri gluten-free, use Umami Sauce, tamari, gluten-free soy sauce, or coconut aminos.
Shiso: Adding fresh, chopped shiso will add an additional layer of taste to your onigiri ... if you're able to find some. Shiso is a classic Japanese garnish with a distinct taste that's hard to describe.
Cheese: I recommend using a semi-hard, mild cheese. After considering a cream cheese, I ended up using a firmer cheese that I could cut into small cubes. I used a Danish cheese called Samsø. Other mild cheeses like Edam, young gouda, Swiss, or some processed cheeses should also pair well with the tuna mayo. Firmer mozzarella also works, but I prefer a semi-firm cheese with a bit more intensity.
Bonito Flakes: Called katsuobushi in Japanese, this is the key ingredient used to make the base for miso soup. Bonito flakes and cheese, I discovered, is not that unusual of a combination. This is another secret ingredient to bring out even more umami in your onigiri fillings. It seems weird, I know. But trust me.
Want to make spicy tuna onigiri?
Adding a few dashes of Tabasco sauce to the tuna mayo mix is guaranteed to give these a spicy kick. Sriracha, I haven't tried but I think it's a safe bet. A Korean-influenced version with gochujang might turn out awesome too.
Or try adding wasabi to mayo like I did in my salmon avocado onigiri fillings recipe. I can guarantee that combo to be life-changing! You'll never think of mayonnaise the same way again.
How to Make Tuna Mayo Onigiri Step-by-Step
For step-by-step instructions, you'll find them in the recipe at the bottom of this post.
Cooking Rice for Onigiri
The key to making delicious onigiri is choosing the right rice and cooking it properly. I used to cook rice in a rice cooker. But after my cooking lesson with Kimono Mom, I've since graduated to making rice in my Kimono Mom donabe.
If you're new to cooking Japanese short-grain rice, these are some resources that will help you not screw up.
- Cooking rice in a donabe: instructional video by Kimono Mom (English subtitles) and easy-to-follow directions on how to cook rice in a donabe
- Cooking rice in a rice cooker: Follow the directions that come with your rice cooker. Or find detailed instructions at justonecookbook.com.
- Cooking rice on the stove: Find detailed instructions at justonecookbook.com.
Pro Tips for Making a Tuna Mayo Filling
Creating a perfect tuna mayo onigiri filling is all about minimizing excess moisture, balance, and texture. Here are some expert tips to help you tick all three of those boxes.
1. Drain the Tuna Well: Whether you choose water or oil-packed canned tuna, it’s crucial that you fully drain the tuna. Too much moisture will result in soggy onigiri that will fall apart. You want to avoid wet rice.
2. Use Japanese Mayonnaise: Japanese mayo, like Kewpie, is available overseas. Kewpie mayonnaise is made with yolks rather than whole eggs, making it richer, and creamier with a more custard-like texture. Also, the taste is slightly sweeter, tangier, and high in umami compared to regular mayo.
3. Add Umami: In my recipe, I used Kimono Mom’s Umami Sauce, which I highly recommend. Otherwise, you can enhance the natural umami in tuna with a small amount of soy sauce. Just be sure to measure carefully so you overpower the tuna.
4. Enhance Flavor and Texture with Add-Ins: This time, I went with chopped shiso, creamy but firm chunks of avocado, and semi-firm (chewy) cubes of mild cheese to upgrade the mouthfeel and add additional layers of flavor.
5. Get Fancy: Chef Mark Sekita gave me this idea. Consider swapping the canned tuna with chunks of sushi-grade maguro to make something really special. In this case, I’d probably leave out the cheese. The avocado, though, is a go!
Making the Perfect Triangular-Shaped Rice Ball
During my own learning curve, I sent a picture of my ugly attempt at an onigiri to my Japanese host mom in Gunma. Basically, her response was that it takes a little practice.
The pretty, photoshopped onigiri you see here were not my first attempt. I’d been testing this recipe every weekend for over a month. And here are some tips to help you learn from all my mistakes!
These pro tips will help you with forming and filling your onigiri for a satisfying and well-structured rice ball:
- Wet Your Hands: This prevents the rice from sticking to your fingers. Now, intuitively, I know when to re-dip my hand in a bowl of water so the rice won’t stick. Initially, I dip my hands in a bowl of water and shake the excess water off. Then, I sprinkle a pinch of salt on one palm and rub my hands together.
- Let the Rice Cool: You know what it’s like to play the game “hot potato”? Ideally, you want your rice to be like that. Let the rice cool enough that it’s not too hot to handle. You should be able to toss it from hand to hand like a hot potato without burning your palms and yelling any swear words.
- Form with “Soft Hands”: You want to squeeze the rice between your palms with only just enough firmness to form it into a ball. For the rice to maintain its light, fluffy texture, avoid squeezing too tightly. Use just enough pressure for the onigiri to maintain its shape.
- Add the Right Amount of Filling: There’s nothing more depressing than biting into an onigiri with a less-than-expected amount of filling. But on the flip side, if you overstuff your onigiri, you’ll have a next-to-impossible time enclosing the filling with rice. That’s why for beginners, I encourage you to err on the side of not enough filling.
- Use a Plastic Wrap: If you have food safety concerns about forming onigiri with your bare hands, you can use the plastic wrap method or an onigiri mold. Last week, I noticed a Japanese cook using plastic wrap to make onigiri. If I'm cooking for guests, I might consider using plastic wrap.
To learn the basics of making simple (and easy) onigiri, check out my recipe for making onigiri with no fillings. It's a lot easier for beginners and requires less time.
How to Wrap Onigiri with Nori Seaweed (for beginners)
These are the most important things to know before wrapping your perfectly formed triangles of rice with nori.
- Keep Nori Fresh and Crispy: To maintain its freshness, store nori in the fridge and avoid exposing it to air until you're ready to use it. When wrapping your onigiri, wait until just before serving to ensure the nori stays crisp. This mimics the technique used by Japanese convenience stores, where onigiri comes in special plastic packaging that keeps the nori separate from the rice until the moment you're ready to eat.
- Toast the Nori: (optional) Lightly toasting the nori over an open flame will revive moist nori, increase crispiness, and bring out the flavor. Some restaurants in Japan do this over a traditional hibachi grill with hot coals.
- Moisten Hands: Before you wrap your onigiri, you may need to lightly dampen your fingers so the rice doesn't stick. You can lightly moisten the nori to help it stick to the rice if needed. Usually, I find it's not needed.
- Cut to Size: Cut a full sheet of nori with kitchen scissors or a sharp knife to the size you need. The standard size for onigiri is ⅓ of a full sheet. Though, it depends on which wrapping technique you use.
- Wrapping Techniques: If you're a beginner, I suggest that you start by simply wrapping a strip around the base of the triangle. Then you can begin to experiment with different wrapping styles that require a bit more practice.
More delicious onigiri recipes
I promise you'll love my other onigiri, like I do, too:
Easiest onigiri recipe (shio salt-flavored Japanese rice balls with no fillings)
Onigiri fillings recipe (salmon, mayo, avocado, and shiso with wasabi mayonnaise)
Passing the inspiration on to you
Because of the inspiring passion and courage I witnessed when meeting Kimono Mom, these onigiri came to life in my kitchen. Reflecting on how all the dots connected for this recipe to reach you feels truly awe-inspiring—it’s a blessing to share it with you.
This tuna mayo onigiri recipe combines nostalgic flavors, creamy textures, and umami-packed goodness. Whether you’re new to making onigiri or a seasoned Japanese home cook ready to elevate your rice ball game, I hope this recipe has sparked inspiration for you.
Have you tried making onigiri before? What’s your go-to filling? Share your thoughts and creations in the comments—I’d love to hear your ideas and see how you make this recipe your own!
Frequently Asked Questions about Tuna Mayo Onigiri
Is tuna mayo onigiri healthy?
Tuna mayo onigiri are relatively healthy for most people. Tuna is nutritious and high in protein. However, it's important to be aware of tuna's mercury content. Light tuna has the lowest mercury level compared to other species: yellowfin, albacore, and bigeye (Healthline).
How long does tuna mayo onigiri last?
Onigiri taste best when they're fresh. Onigiri made with mayonnaise can be stored in the fridge overnight. To be safe, I wouldn't consume if it's been more than one day. Personally, I wouldn't want to eat a tuna mayo onigiri that's been in the fridge longer than one day.
When should you not eat canned tuna?
The FDA recommends that women who are pregnant or breastfeeding avoid fish that are high in mercury (Healthline). It's also advisable to not consume more than 2-3 servings of canned tuna per week for adults. For children, please see the healthy fish consumption guidelines according to the child's age.
Tuna Mayo Onigiri + Avocado and Cheese
Ingredients
Rice
- ¾ cup Japanese short-grained rice equal to one "rice cooker cup"
- 200 ml water ⅞ US cup
- ¼ tsp salt fine-grain sea salt or kosher salt
Filling (& Topping)
- 1 can canned tuna oil or water-packed
- 1 tsp Umami Sauce by Kimono Mom
- 1 Tbsp Japanese mayonnaise
- 3 leaves fresh shiso (perilla leaf)
- 30 grams firm, mild cheese ⅓ cup
- 1 Tbsp bonito flakes about 1 g
- ½ avocado small to medium-sized
Wrap
- 1 sheet dried nori seaweed
Instructions
Cooking Rice
- Cook rice according to your rice cooker's directions or check out my suggestions on how to cook Japanese rice in the notes below.
Making the Filling
- Open can of tuna and drain out as much of the liquid as possible.
- Scoop tuna into a medium-sized bowl.
- Add Umami Sauce to tuna and stir.
- Add Japanese mayonnaise and mix together until all the mayonnaise is mixed into with the tuna.
- Rinse clean and dry shiso leaves. Cut into small pieces about 1 cm by 1 cm. Add to the tuna mayo and mix well.
- Cut cheese into small cubes (approx. 1 cm by 1 cm). Put in a separate bowl.
- Add bonito flakes on top of cheese cubes.
- Drizzle a few drops of Umami Sauce on top (about ¼ tsp) and mix to coat the cheese with bonito flakes evenly.
Preparing Rice
- Transfer freshly cooked rice from your rice cooker or pot to a large bowl or glass baking dish.
- Using a spatula, gently spread out the rice to cover the bottom of your bowl.
- Sprinkle with salt (¼ tsp) and mix into rice by lightly tossing and folding over using a spatula.
- Cool the rice until you no longer see clouds of steam and the rice has cooled just enough that you can hold it in your bare hands.
Shape Onigiri by Hand
- Fill a bowl with room temperature water and a small dish with salt. Keep these nearby to use as needed.
- Using your spatula, divide the cooked rice into three equal sections in your bowl or pan.
- Dip both of your (immaculately clean) hands into your bowl of water. Shake off the excess water.
- Using your hands or spatula, scoop up enough rice to make one onigiri.
- First, like making a snowball in two hands, gently form the rice into a sphere. Make it a ball shape but not too compact.
- Press the center of your ball of rice to make an indentation. Make it deep and wide. You want ample space to stuff lots of filling.
- Stuff fillings inside the indented space. You can use a spoon, chopsticks, or your fingers to press the fillings in to make space for adding more until the space is completely full and compacted.
- Cup the palms of your hand to enclose the filling inside the indented space, closing the opening tightly until you can no longer see the fillings.
- Place the sphere of rice in the palm of your non-dominant hand. Bend your palm to make a v-shaped "valley".
- Bend the fingers of your other hand to make an upside-down v-shape. Cover the rice ball with your V-shaped dominant hand. Your dominant hand makes a "mountain" to cover the rice— think Mt. Fuji.
- Then, gently squeeze the rice ball with your top v-shaped hand to form one corner of a triangle.
- Next, flip the rice ball 90 degrees towards you. The first corner of your triangle should now be resting on the palm of your bottom hand.
- Again, gently squeeze with your top, v-shaped hand to form another corner to make a triangle.
- Repeat this rotate and squeezing process until you've made a neat triangle shape.
Wrapping Onigiri with Nori Seaweed
- Cut nori seaweed sheet into strips with a sharp knife or kitchen scissors. I prefer to cut strips ⅓ of a full-size sheet. Trim strips shorter so the nori will cover ⅔s of each side of onigiri.
- Hold the onigiri in one hand. Place the strip of nori under the bottom edge of the rice ball, shiny side out and rough side against the rice.
- Wrap the ends of the nori up along the sides, pressing gently to secure it in place.
- Stand the onigiri vertical on a plate.
- Use a small spoon, chopsticks, or your fingers to create small divots (about 1 cm deep) in the top corners of each onigiri.
- Carefully place extra fillings into the divots, adjusting as needed to keep the toppings balanced and secure.
- Serving onigiri warm for the best taste. Or, set them aside to let them cool to room temperature.
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