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Tuna Mayo Onigiri

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Tuna Mayo Onigiri is simply a delicious triangular-shaped rice ball with tuna and mayonnaise filling and nori sheet strip. It is very easy to make and very versatile for lunches or even picnic food. In addition, Tuna Mayo Onigiri is very fun to make. I made these with some friends and decorated the onigiri with some facial emojis with a nori sheet. Cute right?

tuna mayo onigiri

The filling can be anything, but my favorite is tuna mayo filling. The reason is probably that tuna and mayonnaise are always in my kitchen pantry. Morovere, tuna mayo is generally one of the most popular onigiri flavors that you can buy in convenience stores in Japan.

What Rice Do You Use for Onigiri?

Not many ingredients are required to make Tuna Mayo Onigiri. All you need is some warmed cooked rice, salt, tuna, and mayonnaise. The best rice for making onigiri is short-medium grain rice that is often labeled as Japanese rice or sushi rice. This is because of the consistency and flavor of Japanese rice are different from other types of rice. The advantage of using Japanese rice is it becomes sticky when cooked, which helps onigiri to hold together and not fall apart.

One great tip for making onigiri is to make sure your rice is still warm because cold rice can lose its stickiness. Cook your rice and let it cool enough to handle. Shape and fill your onigiri, and then let them cool to room temperature before wrapping the seaweed. This will prevent the seaweed from getting soggy.

How to Shape Onigiri

Onigiri comes in many shapes and forms, but the triangular one seems to be the most popular. Shaping the onigiri may seem intimidating, but it is actually easier than it looks. There are 3 ways how to shape onigiri:

1. By hand

Firstly, have a bowl of salted water set up and wet your hands. This will prevent the rice from sticking and the salt will season the rice. Spread a handful of warm rice into one hand. Place the filling in the center and fold up the rice around the filling. Then, pack the rice tightly with both hands into a triangular shape.

2. Using a mold

There are actually molds made for making onigiri. I usually use a mold because it is easier and faster. Moreover, I want to make sure the size of onigiri is exactly the same as each other. I have onigiri molds in two different sizes. I usually use the big one for making onigiri with filling, while the smaller one is for plain or mixed-rice onigiri with no filling If you do not have one, do not worry because you can use cookie-cutters to shape the onigiri. Let me guide you on how to use them below.

  • Using onigiri mold: Salt the rice directly, since you are not using salted water on your hands. Rinse your mold with water and fill halfway with rice. Make a little dent in the center and add the filling. Cover the filling with more rice. Cover the rice mold with the lid and press down. Remove the lid, invert the mold, and press the button to release.
  • Using cookie cutter: Salt the rice directly. Moisten the cookie cutter and place it over a parchment paper. Press rice into the mold halfway. Form a small hole in the center and place your filling in it. Fill the rest of the mold with rice and pack it tightly.
tuna mayo onigiri
how to make onigiri

3. Using a plastic wrap or kitchen towel

This plastic wrap method is great to save the plastic to wrap up and store the onigiri. Salt the rice directly. Spread the rice on the plastic wrap or kitchen towel. Tuck the filling at the center, and gather the plastic/towel up so that the rice surrounds the filling. Twist and squeeze the plastic/towel so that when you unwrap it, the onigiri should be well-packed.

How to Store Tuna Mayo Onigiri

I really recommend eating Tuna Mayo Onigiri on the same day they are made because the filling contains mayonnaise. If you do not have time in the morning, it is okay to make them the night before. You can keep them in the refrigerator, but do not keep them for more than a day.

Be sure not to skip adding salt to the rice because salt helps to preserve the freshness of the rice. In addition, do not wrap the nori if you intend to put onigiri in the refrigerator because the seaweed will get soggy the next day. Wrap onigiri in plastic wrap before storing them in the refrigerator to keep the moisture in so that the rice will not get dried up. Then, you can warm them up a little in the microwave then wrap them in nori before eating.

tuna mayo onigiri

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tuna mayo onigiri
5 from 3 votes

Tuna Mayo Onigiri

Tuna Mayo Onigiri are simply a delicious triangular-shaped rice balls with tuna and mayonnaise filling and nori sheet strip.
Author: Jaja Bakes
Course: Side Dish, Snack
Cuisine: Japanese
Servings: 5 onigiri
Tap or hover to scale!
Prep Time20 minutes
Cook Time10 minutes
Total Time30 minutes


  • 4 cups steaming short-medium grain rice
  • 1/2 tsp salt, to taste
  • 1 sheet nori seaweed
  • Vegetable oil
  • 3.5 oz (100 gr) tuna steak
  • 1 1/2 tbsp Japanese mayonnaise
  • 1/2 tbsp soy sauce


  • Cut nori sheet into 5 10x3cm small strips.
  • Put the steaming rice into a big bowl. Sprinkle the salt evenly and mix until well combined. Let the rice cool slightly until warm enough to handle. Do not cool the rice completely. Set aside.
  • Cut tuna into small pieces. Heat a frying pan on medium heat. Add a little bit of oil and cook tuna until fully cooked. Turn off the heat and transfer to a medium bowl.
  • Using a fork, break tuna into flakes. Stir in mayonnaise and soy sauce and well combined. Set aside.
  • Wet your hand and onigiri mold so that the rice does not stick. Add rice halfway into the mold. Add a little dent in the center and fill with tuna mayo. Cover the filling with more rice until of the way 3/4 full. Press the lid down until firm. Push your thumb into the mold bottom to release the onigiri.
  • Wrap the onigiri with nori strips and serve.


If not eaten immediately, wrap onigiri in plastic wrapping to keep them moist.
Do not wrap the nori if you intend to put the onigiri in refrigerator because the nori will get soggy.
You can warm them up a little in microwave then wrap them in nori before eating.


Serving: 1onigiri | Calories: 240kcal | Carbohydrates: 34g | Protein: 8g | Fat: 8g | Saturated Fat: 1g | Polyunsaturated Fat: 4g | Monounsaturated Fat: 2g | Trans Fat: 0.03g | Cholesterol: 9mg | Sodium: 378mg | Potassium: 69mg | Fiber: 1g | Sugar: 0.1g | Vitamin A: 462IU | Vitamin C: 0.2mg | Calcium: 14mg | Iron: 3mg
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5 from 3 votes (1 rating without comment)

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Recipe Rating


  1. 5 stars
    These rice balls were so tasty and easy to make – and I say that as someone who has never had a rice ball in her life lol
    I did have to use canned tuna because I couldn’t get fresh….. but it was still really tasty.
    I can’t wait to try salmon rice balls and all the other rice balls – I will have to buy a mold since I plan on making these a lot in the future.
    My 2 year old also really enjoyed them and she doesn’t usually eat rice!
    Thanks for the recipe!