Portugal Dual Citizenship for Americans and Britons Explained

Yes. An American or a Briton who naturalizes in Portugal can keep the first citizenship: the Portuguese Ministry of Justice says Portuguese law lets a Portuguese national hold other nationalities, and neither the U.S. nor the UK government asks you to choose. What a second passport changes is practical: which passport you show at which border and what consular help you can expect. For an American it does not appear to change the U.S. tax return.

This guide goes into the dual nationality questions that the citizenship guide for Americans and Britons only states in a few lines. It rests on the State Department, USAGov, GOV.UK, IRS and Portuguese Ministry of Justice pages, all read on 18 October 2026. The most recent date on those pages that the text relies on is 4 October 2026, the day the IRS marked its expatriation tax page as reviewed or updated; the USAGov page was last updated on 17 March 2026. It is a reading of official wording, not legal advice.

Does Portugal let me keep my American or British citizenship?

Yes, as far as the Portuguese side goes. The Ministry of Justice guide “Como obter a nacionalidade portuguesa” says that Portuguese law allows a Portuguese national to have other nationalities, so you do not need to give up another nationality to acquire the Portuguese one. The same guide adds a warning that points the other way: the laws of other countries may require you to give up Portuguese nationality in order to hold theirs. The guide is marked “under update” and its information was last updated on 3 July 2025.

Article 8 of the Nationality Law, as consolidated on the Diário da República, says that, without prejudice to what the law provides, Portuguese nationality is lost by those who, being nationals of another state, declare that they do not want to be Portuguese. The page shows article 8 as amended by Organic Law 1/2026, in force from 19 May 2026. Holding another nationality does not by itself cost you Portuguese nationality under that article; the loss follows a declaration to that effect.

Neither the U.S. nor the UK is one of those countries, as the next two sections show. If you are not yet at the naturalization stage, the way in starts with the guide to residence routes for Americans and Britons.

What do the U.S. and UK governments say about holding a second nationality?

USAGov, the U.S. government’s information portal, says the same in shorter form: you owe allegiance to both countries, must use a U.S. passport to enter and leave the U.S., do not have to choose one nationality over the other, and may naturalize in another country without risking U.S. citizenship. It adds that eligibility for a second citizenship depends on the policies of the second country, which in your case means Portugal’s. The State Department page says nothing about Portugal in particular.

Which passport do I use, and what help can I get abroad?

The pages are specific on the home-country side.

• Americans: the State Department says U.S. nationals, including dual nationals, must use a U.S. passport to enter and leave the United States. It adds that dual nationals may also be required by the country of their foreign nationality to use that country’s passport to enter and leave it, and that using the foreign passport to travel to or from a country other than the United States is not inconsistent with U.S. law.
• Britons: GOV.UK says a dual national can travel to the UK using a valid UK passport or Irish passport, or a certificate of entitlement. It also says you cannot get an electronic travel authorisation (ETA) if you are a British or Irish dual citizen. The same page says that someone who is not a British citizen needs permission to travel to the UK, for example an ETA, so a UK or Irish passport or a certificate of entitlement is the usual route in for a British dual national. The page also covers travel on an expired UK passport issued in 1989 or later, with a valid ETA-eligible passport, and travel on another passport for people who became British after settling in the UK under the EU Settlement Scheme.

On consular help, both governments warn about the country of the other nationality. The State Department says dual nationals “may also face restrictions” in the U.S. consular protections available to them abroad, “particularly in the country of their other nationality”, and that claims of other countries on a dual national may result in conflicting obligations. GOV.UK says a dual national cannot get diplomatic help from the British government in the other country where they hold citizenship, and its example is a person with British and French citizenship in France. Both pages speak about any country of your other nationality. After naturalization, that country is Portugal.

The State Department also says dual nationals owe allegiance to both countries, are required to obey the laws of both, and that either country has the right to enforce its laws.

Does Portuguese citizenship change my U.S. taxes?

The IRS page does not link U.S. tax obligations to how many nationalities you hold. It links them to being a U.S. citizen or resident alien. The IRS page “U.S. citizens and resident aliens abroad” says that, if you are a U.S. citizen or resident alien, the rules for filing returns and paying estimated tax are generally the same whether you are in the United States or abroad, and that you are subject to tax on worldwide income from all sources. It also says that many Americans abroad qualify for special benefits, such as the foreign earned income exclusion and foreign tax credit, but get them only by filing a relevant U.S. return, and that foreign accounts above the reporting threshold must be reported on an FBAR even if they produce no taxable income. The page was marked reviewed or updated on 28 September 2026.

Nothing on the page says that taking a second nationality lowers or ends those obligations, so a Portuguese passport does not appear on the page as a factor. The consequences for your own file, including exclusions, credits and account reporting, are set out in our guide on whether Americans still file U.S. taxes from Portugal.

Britons: the GOV.UK dual citizenship page does not discuss tax, and we did not read HMRC pages for this guide.

What if I want to give up my American or British citizenship?

You do not need to for Portugal. If you want to for another reason, the two governments say very different things.

• United Kingdom: GOV.UK says you can apply to renounce your British citizenship, and if accepted you get a declaration of renunciation. You can only do this if you already have another citizenship or nationality, or you are going to get one after giving up British citizenship. You must be 18 or over (unless under 18 and married) and of sound mind (unless it is decided that it is in your best interest). The page says your right to live in the UK will be affected, and that giving up your citizenship only affects you and not other family members, although it could affect the status of children you have in future.
• United States: the pages we read do not describe the renunciation procedure. The IRS page on expatriation tax says that expatriation tax rules apply to U.S. citizens who have renounced their citizenship, and that a citizen is treated as relinquishing U.S. citizenship on the earliest of four dates, tied to steps with the State Department or a court. It defines a “covered expatriate” as someone who meets any one of these: an average annual net income tax for the five prior years above a threshold ($206,000 for 2025), a net worth of $2 million or more on the date of expatriation, or a failure to certify on Form 8854 that all federal tax obligations for the five preceding years were met. For covered expatriates, property is generally treated as sold at its fair market value the day before expatriation, and the gain this produces is reduced by an exclusion amount ($890,000 for 2025). The IRS also says a $10,000 penalty may be imposed for failing to file Form 8854 when required. The page was marked reviewed or updated on 4 October 2026.

This is an information summary. A decision of this size, for an American, belongs with a U.S. tax professional before any step is taken.

What about a spouse or children?

Nationality does not pass automatically in every direction, and the pages say so. GOV.UK says you do not automatically become a British citizen when you marry one; you need to apply as the spouse of a British citizen. It adds that in some countries a married person is automatically counted as having their partner’s nationality and that children may automatically have a parent’s nationality even if born abroad, and tells you to check with the country’s consulate or high commission.

The State Department says a person may be a dual national by automatic operation of different countries’ laws rather than by choice, for example a child born in a foreign country to U.S. national parents. It also says that if a foreign country’s law permits parents to apply for citizenship on behalf of minor children, nothing in U.S. law impedes U.S. citizen parents from doing so. Whether Portuguese law gives your spouse or child a route is a question for the Portuguese nationality pages and the registry, not for these governments.

More guides on this site: passport renewal and consular services.

What should I check before I apply?

Related guides: citizenship by residence, step by step and the Portuguese language requirement and how to prove it.

Related guides: what changed in the nationality law in 2026 and what to check before you apply.

Official pages read for this guide: the U.S. Department of State “Dual Nationality” page, USAGov “How to get dual citizenship or nationality”, GOV.UK “Dual citizenship”, GOV.UK “Give up (renounce) British citizenship or nationality”, the Portuguese Ministry of Justice guide “Como obter a nacionalidade portuguesa”, the IRS pages “U.S. citizens and resident aliens abroad” and “Expatriation tax”. All were read on 18 October 2026.