2025-10-24

Basically, everyone has a nationality. However, how nationality is determined and the underlying concepts vary from country to country. Here, we explain what happens when a Japanese person acquires dual nationality.

What is Nationality?

What exactly is “nationality”?

Generally, “nationality” is interpreted as the qualification that allows a person to become a ‘member’ of a specific country. Here, “member” refers to each individual who makes up a specific organization or group.

For a country to exist, it requires national territory (land) and citizens who make up the nation. In other words, without territory and citizens, the state itself cannot exist.

Therefore, every nation has the concept of “nationality”—the qualification to become a citizen of that country. Furthermore, all nations define nationality based on their own criteria and laws.

However, since countries differ in their history, culture, traditions, and political/economic situations, the way nationality is defined also varies. In other words, each country establishes its own criteria and rules for nationality based on its own judgment.

Rules for Determining Nationality

Under Japanese law, if either the father or mother holds Japanese nationality, their child acquires Japanese nationality. Even if the child is born overseas, they possess Japanese nationality as long as one parent holds it.

In other words, Japanese law mandates that regardless of the country of birth, if either parent is Japanese, the child automatically holds Japanese nationality. This principle is called “jus sanguinis” (bloodline principle).

In contrast, under U.S. law, children born within the United States are granted U.S. nationality, regardless of their parents’ nationality. This approach bases nationality on the country (territory) of birth, not the parents’ nationality. This concept is called “jus soli” (birthright citizenship).

What if you have dual nationality in Japan?

For example, a child born to Japanese parents residing in the United States would hold both U.S. and Japanese nationality under the laws of both countries.

Japanese law does not recognize dual nationality. However, if a “Declaration of Reservation of Nationality” is submitted to the Japanese embassy or consulate in the United States within three months of birth, the child can retain both Japanese and American nationality. If this declaration is not made, the child cannot retain Japanese nationality and will only hold American nationality.

The above system is a temporary, expedient measure allowing dual nationality to preserve the possibility of holding Japanese nationality should a child born in the United States later return to Japan. However, if the child lives in Japan, they must choose either Japanese or American nationality, as Japan does not recognize dual nationality.

Summary

If either parent is Japanese, a child born to that couple in the United States will hold dual nationality (Japanese and American). However, if the child lives in Japan, they must choose one nationality.