2025-08-29

International marriages are becoming more common in Japan. This naturally raises the question: what happens to your last name (family name) after marriage? There are several patterns regarding last names, so let’s explain in detail.

International Marriage and Nationality

Even when a Japanese national marries a foreign national, neither party’s nationality changes due to the marriage. Unless they actively change their nationality, it remains the same.

However, after marriage, the foreign national can apply for naturalization and acquire Japanese nationality. In this case, being in an international marriage tends to make the application more likely to be approved than if the person were single.

Principles of Surnames in International Marriage

Japan has a system called the “family register” (koseki). When two Japanese nationals marry, a new family register is created for the couple. Since the family register only allows one surname, Japanese couples will share the same surname.

Only Japanese nationals can have a family register created. Therefore, foreigners do not have a family register, and even if they marry a Japanese national, no family register is created for them.

This means that when a Japanese person marries a foreigner, neither the Japanese nor the foreign spouse changes their surname unless specific procedures are followed. Consequently, the couple retains separate surnames. However, by completing certain procedures, a Japanese spouse can adopt the same surname as their foreign spouse.

Three Options

Japanese citizens married to foreigners have three options for adopting their spouse’s surname:

The first option is to adopt the foreign spouse’s surname (family name). For example, if “Suzuki Yoko (Japanese)” marries “James Washington (American),” she would change her name from “Suzuki Yoko” to “Washington Yoko.”

In this case, a “Notification of Change of Family Name” must be submitted to the municipal office within six months of the marriage. If the procedure is done after six months, a petition for the change must be filed with the family court.

Note that “Suzuki Yoko” retains Japanese nationality while adopting her spouse’s surname (Washington). This also necessitates changing her family register entry (from “Suzuki Yoko” to “Washington Yoko”).

The second method involves a foreign national adopting a Japanese surname. Using the previous example, this would be changing from “James Washington” to “Suzuki James”.

In this case, the laws of the foreigner’s home country must first be confirmed. While Japanese citizens marrying foreigners generally retain separate surnames, if the home country’s laws mandate a surname change, it will occur. This case involves changing the foreigner’s legal name, requiring procedures in their home country.

If the home country’s law stipulates that the surname does not change upon international marriage, and the Japanese spouse wishes to use the Japanese surname, they can register a “common name” at their local municipal office in Japan. This common name can be used solely within Japan.

Finally, the third case involves adopting a compound surname. Using the earlier example, this would be changing to “Washington Suzuki Yoko”.

In this case, an application must be filed with the Family Court with jurisdiction over the applicant’s place of residence. Name changes are permitted when there is a legitimate reason or unavoidable circumstances. When filing the petition, you must submit a statement of reasons, documentation showing the basis for using the compound surname in the other country, and evidence of its use, such as mail.

Summary

In international marriages, the default is separate surnames for spouses. However, many couples likely wish to adopt one partner’s surname or a combined surname after marriage. Since procedures differ for each option, carefully consider your choice before proceeding.