Last updated: June 18, 2026.
How this page is sourced: We separate the U.S. citizenship answer from the second-country answer because those are controlled by different laws. Claims about U.S. nationality, passport use, tax filing, FBAR, and consular limits are linked beside the relevant text to official or primary sources where available. Movingto's editorial process and corrections policy explain how we handle updates and fixes; this page is general information, not legal advice.
Dual citizenship means one person is treated as a citizen or national by two countries at the same time. For Americans, the practical question is not whether the United States has a special "dual citizenship application." It does not. The real question is whether U.S. citizenship and another country's citizenship overlap, and what duties each country still applies to you.
U.S. answer vs second-country answer
| Question | U.S. answer | Second-country answer to check |
|---|---|---|
| Can I keep U.S. citizenship? | Usually yes. U.S. law focuses on voluntary expatriating acts done with intent to relinquish U.S. nationality. See 8 U.S.C. 1481. | The other country may allow, restrict, or prohibit dual citizenship, and may require a renunciation step. |
| Which passport do I use? | Use a valid U.S. passport to enter and leave the United States. See 8 U.S.C. 1185 and the State Department dual-nationality guidance. | The other country may require you to use its passport at its border if it also treats you as a citizen. |
| Do U.S. tax rules stop? | No automatic stop. U.S. citizens abroad generally remain in the U.S. tax system on worldwide income. See the IRS guidance for U.S. citizens and resident aliens abroad. | The other country may tax residents, citizens, local income, assets, or gains under its own rules. |
| Do foreign accounts matter? | They can. FBAR can apply when aggregate foreign-account values exceed $10,000 at any time during the calendar year. See IRS FBAR guidance and FinCEN FBAR guidance. | Local banks may have tax-residency, reporting, or account restrictions for U.S. persons. |
| Can the U.S. help me abroad? | Often, but not always in the same way. The State Department warns that consular access can be limited when the other country also treats you as its citizen. See State Department dual-nationality guidance. | The other country may treat you only as its own citizen while you are inside its territory. |
| Is the second citizenship actually valid? | The United States does not certify the foreign citizenship for you. | Use the foreign ministry, immigration authority, embassy, or consulate as the controlling source. |
The U.S. rule: dual citizenship does not usually mean losing U.S. citizenship
The U.S. rule is usually permissive, but it is not a blanket answer for every country. U.S. nationality law lists acts that can cause loss of nationality only when done voluntarily and with the intention of relinquishing U.S. nationality, including certain foreign naturalizations and formal renunciation. See 8 U.S.C. 1481.
The United States also does not issue a separate dual-citizenship certificate. A person can become a dual citizen when U.S. citizenship and another country's citizenship overlap. That can happen at birth, through a parent, through naturalization abroad, or when a foreign national naturalizes in the United States and their original country allows them to keep that citizenship.
Do not treat online summaries as personal legal advice if you are planning to renounce, have already taken a foreign oath that includes renunciation language, work in a sensitive government role, or face a citizenship dispute. Those are situations for an immigration or nationality lawyer who can review the exact facts and documents.
Common ways Americans become dual citizens
| Route | How it can happen | Main check |
|---|---|---|
| Birth in the United States plus another nationality | A person born in the United States may be a U.S. citizen and may also acquire another nationality through a parent or foreign law. | Confirm whether the parent's country recognizes citizenship by descent and whether it allows dual citizenship. |
| Birth abroad to a U.S. citizen parent | Some children born abroad acquire U.S. citizenship at birth when statutory requirements are met. USCIS summarizes acquisition rules in its USCIS citizenship-at-birth policy. | Keep birth, parentage, residence, and consular records because evidence matters later. |
| Naturalizing in another country | A U.S. citizen may naturalize abroad, but U.S. loss-of-nationality analysis depends on the act and intent. The statutory source is 8 U.S.C. 1481. | Check both U.S. intent rules and the foreign naturalization oath or renunciation requirement. |
| Marriage or partnership | Marriage can create a residence or naturalization path in some countries, but it rarely grants citizenship automatically on the wedding date. | Read the foreign government's official naturalization and residence requirements before assuming eligibility. |
| Investment or citizenship programs | Some countries offer citizenship or residence routes tied to investment, donation, or economic contribution. | Confirm the program is an official government route, whether citizenship is direct or follows residence, and whether dual citizenship is allowed. |
| Naturalizing in the United States as a foreign national | A foreign national applies for U.S. naturalization through USCIS Form N-400. The United States does not decide whether the applicant's original country lets them keep that prior citizenship. | Check the original country's nationality law before assuming dual citizenship remains possible. |
U.S. duties that can continue after dual citizenship
The U.S. side of dual citizenship is mostly about continuing duties. It is common for the U.S. citizenship answer to be "yes" while the practical answer is "yes, but check the duties first."
Passport use
When you travel internationally, you may have more than one passport, but the United States has a specific rule for U.S. citizens. A U.S. citizen must bear a valid U.S. passport when entering or departing the United States under 8 U.S.C. 1185. The State Department makes the same practical passport point in its State Department dual-nationality guidance. That rule is separate from how your other country asks you to enter or leave its territory.
A practical example: if you are a U.S. and Portuguese citizen, you would normally use your U.S. passport for the U.S. border and your Portuguese passport for Portugal or EU entry. That does not mean every trip is risk-free. Name mismatches, expired passports, visa records, or airline check-in systems can still cause problems, so keep both passports current and consistent where possible.
Tax filing and foreign accounts
Dual citizenship does not switch off U.S. tax filing duties. The IRS states that U.S. citizens and resident aliens abroad generally have the same income tax filing requirements as people living in the United States, and that worldwide income is in scope. See the IRS guidance for U.S. citizens and resident aliens abroad. Depending on your income, residence, and treaty position, you may be able to use exclusions, credits, or treaty relief, but those are filing positions rather than an automatic exemption.
Foreign accounts are a separate issue. A U.S. citizen with foreign financial accounts may have FBAR reporting obligations when the aggregate value of foreign financial accounts exceeds $10,000 at any time during the calendar year. Use the IRS FBAR guidance and FinCEN FBAR guidance before assuming that a local bank account abroad is administratively harmless.
Consular help, service obligations, and sensitive work
If you are inside the other country of nationality, local authorities may treat you as their citizen and U.S. consular access can be limited. See the State Department dual-nationality guidance. Almost all male U.S. citizens and male immigrants ages 18 through 25 must register with Selective Service, and another country may have its own military or civic-service rules. U.S. registration rules are summarized by Selective Service registration guidance.
Dual citizenship is not automatically disqualifying in every security-sensitive context, but foreign preference, foreign influence, and use of a foreign passport can matter. Ask the agency, employer, or security officer for the exact rule before using a foreign passport or making foreign-citizenship decisions in that context.
What to check before relying on dual citizenship
| Issue | Why it matters | Primary source or practical check |
|---|---|---|
| U.S. passport use | A U.S. citizen must use a valid U.S. passport to enter and leave the United States, even if they also hold another passport. | 8 U.S.C. 1185 |
| U.S. tax filing | U.S. citizens and resident aliens abroad generally remain subject to U.S. income tax filing rules on worldwide income. | IRS guidance for U.S. citizens and resident aliens abroad |
| FBAR and foreign accounts | Foreign bank and financial accounts can create separate reporting obligations, even when no tax is due. The common FBAR trigger is aggregate foreign-account value exceeding $10,000 at any time during the calendar year. | IRS FBAR guidance and FinCEN FBAR guidance |
| Loss of U.S. nationality | Having another citizenship is not, by itself, the usual problem. The key legal question is whether a potentially expatriating act was voluntary and done with intent to relinquish U.S. nationality. | 8 U.S.C. 1481 |
| Consular help abroad | If you are inside the other country of nationality, local authorities may treat you as their citizen and U.S. consular access can be limited. | State Department dual-nationality guidance |
| Security clearance and sensitive work | Dual citizenship is not automatically disqualifying in every context, but foreign preference, foreign influence, and use of a foreign passport can matter in security-sensitive roles. | Ask the agency, employer, or security officer for the exact rule that applies to the role. |
| Military or service obligations | Almost all male U.S. citizens and male immigrants ages 18 through 25 must register with Selective Service, and another country may have its own military or civic-service rules. U.S. registration rules are summarized by Selective Service registration guidance. | Check both countries before assuming a second citizenship has no service duties. |
| The second country's dual-citizenship law | The U.S. position does not force another country to allow dual citizenship. USA.gov gives the same high-level warning in its USA.gov dual citizenship guidance. | Use the foreign ministry, immigration authority, embassy, or consulate as the controlling source. |
Common mistakes Americans make with dual citizenship
- Using the wrong passport at the U.S. border. A U.S. citizen should not plan to enter or leave the United States on a foreign passport. Use the U.S. passport rule in 8 U.S.C. 1185 and the State Department dual-nationality guidance as the starting point.
- Assuming U.S. tax filing ends after moving abroad. Dual citizenship, residence abroad, or another passport does not automatically end U.S. filing duties. Start with the IRS guidance for U.S. citizens and resident aliens abroad and get tax advice before changing filing positions.
- Assuming marriage equals citizenship. Marriage may support a residence or naturalization route in some countries, but it usually does not create citizenship by itself on the wedding date.
- Relying on old country rules. Nationality laws change. Use a current foreign government, embassy, or consular source before assuming descent, restoration, or dual-citizenship rights still work the same way.
- Ignoring sensitive job or clearance procedures. If you work in a role with security, defense, government, or export-control sensitivity, ask the agency, employer, or security officer before using a foreign passport or making foreign-citizenship decisions.
- Expecting full U.S. consular protection everywhere. The State Department warns that help can be limited when you are in the other country that also treats you as its citizen. See the State Department dual-nationality guidance.
For Americans considering Portugal or EU citizenship
Portugal and EU citizenship planning is separate from the U.S. permission question. For an American, the U.S. answer is usually that dual citizenship can be kept unless there is a voluntary act with intent to relinquish U.S. nationality. The Portugal answer depends on Portuguese nationality law, residence history, language and integration rules, and the route you use. Portugal's official nationality service page is useful for process access, but it is marked as being revised; pair Portugal's official nationality service page with the formal text of Lei Orgânica n.º 1/2026 and the Presidency promulgation notice. Lei Orgânica n.º 1/2026 made the standard naturalization residence period 10 years for nationals of other states and 7 years for EU or CPLP nationals, with previous rules continuing for pending applications.
Movingto has separate practical guides for the Portugal D7 Visa and the Portugal Golden Visa. Use those for residence-route background only; do not rely on any residence guide as the final source for Portuguese nationality timing after the 2026 law change. Verify citizenship eligibility against official Portuguese guidance before relying on any timeline.
Before you apply: document checklist
- Check that your U.S. passport is valid for the travel you expect to make, because U.S. citizens must use a valid U.S. passport to enter and leave the United States.
- Collect birth, parentage, adoption, marriage, divorce, name-change, and naturalization records that support the route you plan to use.
- If the claim is through a U.S. citizen parent, collect evidence tied to the citizenship-at-birth rules summarized in the USCIS citizenship-at-birth policy.
- Save the current foreign government or embassy source that says you are eligible and that dual citizenship is allowed or explains any renunciation requirement.
- Review U.S. tax filing and FBAR exposure before opening accounts, moving assets, or assuming a second passport changes U.S. reporting duties.
- Check whether the second country creates tax, military, civic-service, inheritance, or family-law duties once it treats you as a citizen.
- Get legal or tax advice before signing a renunciation-style oath, applying for a child, changing tax residence, or using a foreign passport in a sensitive job context.
When to get professional advice
Get advice before taking an irreversible step, signing a foreign oath that appears to renounce other citizenships, relying on a passport for a child, moving assets across borders, or making tax filings in two countries. Dual citizenship is often manageable, but the details are personal and document-heavy.
This guide is general information, not legal, tax, or immigration advice. Laws and agency practice can change, and your result can depend on dates, documents, residence history, parentage, and the second country's rules.