Japan does not allow dual citizenship with the US for adults, at least not as a matter of law. Under Japan’s Nationality Act, a Japanese citizen who voluntarily takes on another nationality loses Japanese nationality automatically, and a foreign national who naturalizes in Japan must give up any existing citizenship.1Japanese Law Translation. Nationality Act – English The United States takes the opposite view and has no objection to its citizens also holding Japanese nationality.2U.S. Department of State. Dual Nationality The gap between those two positions, and the further gap between what Japan’s law demands and what its government actually enforces, is what makes the answer more complicated than a straight yes or no.
What Japanese Law Says
Japan operates on a single-nationality principle. Article 11 of the Nationality Act is the key provision: a Japanese citizen who acquires a foreign nationality by choice loses Japanese nationality at that moment.1Japanese Law Translation. Nationality Act – English The loss is automatic. Japan does not need to take any action, hold any hearing, or issue any order. Taking a U.S. naturalization oath is, from Japan’s perspective, the act that ends Japanese citizenship.
The rule works the same way going in. A foreign national naturalizing as Japanese must either have no other nationality or must lose their existing one as a consequence of naturalization.3Ministry of Justice. The Nationality Law A narrow exception exists for applicants whose home country makes renunciation impossible, but the U.S. permits voluntary renunciation, so Americans cannot rely on it.1Japanese Law Translation. Nationality Act – English
What U.S. Law Says
The U.S. side is straightforward. Federal law does not require a citizen to choose between American nationality and any other, and picking up a foreign citizenship does not, by itself, put U.S. citizenship at risk.2U.S. Department of State. Dual Nationality U.S. citizenship can be lost through certain voluntary acts performed with the specific intent to give it up, such as formally renouncing before a consular officer.4USAGov. Renounce or Lose Your Citizenship Merely acquiring Japanese nationality does not qualify.
So the friction is entirely on Japan’s side. Whatever happens next depends on how you came to hold both nationalities.
If You Were Born With Both
The most common way to hold both is by birth. A child born in the United States to at least one Japanese parent typically gets U.S. citizenship under the Fourteenth Amendment and Japanese nationality through the parent. A child born in Japan to at least one American parent can acquire both in the mirror image.
Japan’s Nationality Act tells these dual nationals to pick one. The deadline turns on when both nationalities were acquired. If you became a dual national before turning 18, you must choose by 20. If both nationalities came at or after 18, you have two years from that point.5Consulate General of Japan in Los Angeles. Declaration Registration (Kokuseki Sentaku Todoke) These ages reflect Japan’s April 2022 change lowering the age of majority from 20 to 18.
Choosing Japanese nationality means filing a Declaration of Choice of Nationality at a municipal office in Japan or a Japanese consulate abroad, together with a statement that you intend to renounce the foreign nationality.1Japanese Law Translation. Nationality Act – English Choosing U.S. nationality means renouncing Japanese nationality through a separate consular process.
What Japan Actually Enforces
For dual nationals by birth, the practice is very different from the letter of the law. Japan’s Ministry of Justice has confirmed that no justice minister has ever issued a formal warning to a dual national by birth to choose a nationality, which means no dual national by birth has ever been stripped of Japanese citizenship through the Act’s enforcement mechanism. The government has reportedly sent informational notices to children of international marriages about the obligation to choose, but those are reminders, not legal demands. There is no criminal penalty for missing the deadline. In practice, large numbers of Japanese-American dual nationals hold and use both passports well past the statutory deadlines without consequence.
The picture flips for adults who acquire a second nationality by choice. Article 11’s automatic loss is not theoretical. There have been cases of Japanese citizens who naturalized abroad and then had their Japanese passports invalidated. So the key distinction is not the law on the books but how you came to hold both:
- Born with both: Japan’s enforcement has historically been passive, and many people never file the declaration.
- Acquired the second nationality as an adult: Japanese nationality is lost as a matter of law, and Japan has acted on that loss.
Naturalizing as Japanese
An American seeking Japanese citizenship faces the naturalization requirements in Article 5, including continuous residence in Japan, being of legal age, good conduct, financial self-sufficiency, willingness to give up the current nationality, and no history of plotting against the Japanese government.1Japanese Law Translation. Nationality Act – English The residence requirement has historically been five continuous years, and in early 2026 Japan announced plans to lengthen it to ten years as part of a broader tightening of naturalization standards.
The nationality condition is the decisive one for dual citizenship. An applicant must either hold no nationality or lose the existing one as a result of becoming Japanese.6The Ministry of Justice. Nationality Q&A Because U.S. citizenship is not automatically lost by naturalizing elsewhere, Japan expects American applicants to take affirmative steps to renounce it. Keeping both, lawfully, is not a realistic option for Americans going this route.
Japanese Citizens Naturalizing as American
Going the other direction, the U.S. side raises no obstacle. The U.S. naturalization oath includes language about renouncing foreign allegiances, but the State Department has long held that the oath itself does not cause loss of foreign citizenship, and the U.S. government does not monitor whether new citizens follow through.2U.S. Department of State. Dual Nationality
Japan’s side is the problem. Under Article 11, voluntary acquisition of foreign citizenship ends Japanese nationality at the moment U.S. citizenship is granted.1Japanese Law Translation. Nationality Act – English If the family registry (koseki) is updated to reflect the foreign naturalization, Japanese nationality is formally removed. Some people never report the naturalization to Japan, but using a Japanese passport after nationality has legally been lost creates real exposure, and that exposure grows as information-sharing between the two governments improves.
Permanent Residency as the Practical Answer
For Americans who want to live and work in Japan indefinitely without giving up U.S. citizenship, permanent residency usually solves the problem naturalization cannot. Permanent resident status allows indefinite residence and work in Japan with no nationality requirement, and U.S. citizenship stays intact.
The trade-offs are real. Permanent residents cannot vote in Japanese national elections, cannot run for public office, and cannot hold a Japanese passport. You stay in the immigration system, which means keeping a valid residence card and obtaining a re-entry permit for extended absences. Permanent residency can be revoked for long absences or serious criminal offenses, while naturalized citizenship is rarely reversed except for fraud. The standard path is ten years of continuous residence, with shorter timelines for spouses of Japanese nationals and people with highly specialized skills.
Passports at the Border
If you do hold both nationalities, which passport you present matters. U.S. law requires dual nationals to enter and leave the United States on their U.S. passport, and Japan expects the same in reverse at Japanese immigration. The U.S. Embassy in Tokyo advises carrying both valid passports whenever traveling between the two countries.7U.S. Embassy & Consulates in Japan. Dual Nationality Flying Tokyo to New York, you show the Japanese passport leaving Japan and the U.S. passport arriving in the United States, then reverse on the way back. Airlines may ask to see proof that you can enter your destination before boarding, so keep both accessible.
Recent Court Challenges to the Rule
The dual citizenship ban has been tested in court. A dual national named Yuri Konto argued that Article 11’s automatic loss of nationality violated the Japanese Constitution’s guarantees of equality and the right to pursue happiness. In October 2024, the Fukuoka High Court rejected the challenge, ruling that the Nationality Act’s provisions are constitutional because they are clear, publicly known, and give citizens the chance to choose their nationality in advance rather than stripping it arbitrarily. The court found no unconstitutional discrimination.
That result left the single-nationality principle on solid legal ground. No court has struck down any part of the Nationality Act’s dual citizenship restrictions, and as of 2026, there is no serious legislative momentum in Japan toward permitting dual nationality. If the rule changes, it will change through the Diet rather than the courts, and there is no sign of that yet.