Spain and the United States have no dual nationality treaty. That doesn’t stop thousands of people from carrying both passports, but it does mean each country treats you strictly as its own citizen, and missing one deadline can cost you your Spanish nationality without you ever finding out until it’s too late.
Unlike countries such as the Dominican Republic, which has a formal dual nationality agreement with Spain, the US and Spain have no such treaty. If you acquire one of these nationalities and it isn’t recognized as compatible by the other, you need to take specific steps to protect the nationality you already hold.
If You’re Spanish and You Naturalize as a US Citizen
Under Article 24.3 of the Spanish Civil Code, Spaniards who voluntarily acquire another nationality while habitually residing abroad lose their Spanish nationality by operation of law, unless they take one specific step in time.
The Deadline That Catches People Off Guard
You must go to the corresponding Spanish consulate within three years of acquiring US citizenship and sign the “Declaración de Conservación de la Nacionalidad Española.” Miss the window, and Spanish nationality is lost automatically, with no appeal for the missed deadline itself.
Example: María, a Spanish citizen living in Florida, becomes a naturalized US citizen in March 2024. She has until March 2027 to sign the retention declaration at her nearest Spanish consulate. If she lets the date pass without signing it, she is Spanish only in the sense that she was born Spanish, not in the eyes of the Spanish administration.
In practice, many people never sign it and simply keep renewing their Spanish passport, since consular staff aren’t always required to cross-check US naturalization records at renewal. This isn’t a safe strategy: it works until the day it doesn’t, typically when a legal matter (inheritance, a property sale, a Spanish ID renewal that does get flagged) forces the issue.
How the United States Treats Your Spanish Nationality
The US side works differently. The US places no restriction on holding a second nationality, and naturalizing as Spanish does not put your US citizenship at risk.
But US citizenship comes with an obligation many people overlook: you must file a US tax return every year, regardless of where you live, including from Spain. Depending on your foreign account balances, you may also owe an annual FBAR filing (FinCEN Form 114) to the US Treasury, on top of your regular return.
Which Passport Should You Use?
Once you hold both, day-to-day passport choice matters more than people expect. Use your US passport for most situations, and reserve your Spanish passport strictly for crossing the border into Spain or the EU.
- Present your Spanish passport only when a Spanish or EU immigration officer asks for it at entry.
- Use your US passport for check-in and baggage, even when flying into a Spanish airport.
- Never present the Spanish passport to US immigration authorities, since the US expects its own citizens to enter and exit on a US passport.
Path to Spanish Nationality for US Citizens
If you’re American and don’t yet hold Spanish nationality, you can apply for it through residency under Article 22 of the Civil Code.
- 10 years of continuous, legal residency for most nationalities, including US citizens.
- 2 years for nationals of Ibero-American countries, Andorra, the Philippines, Equatorial Guinea, or people of Sephardic origin.
- Residency must be continuous and lawful, so long trips abroad or gaps between permits can reset the count.
Example: Robert, an American who has held a non-lucrative visa in Spain since 2016 without significant interruptions, reaches his 10-year mark in 2026 and can apply for Spanish nationality by residence that same year, provided he also passes the required language and culture exams.
The two residency routes most commonly used by American citizens are the digital nomad visa and the non-lucrative visa. We’ve covered both in detail:
Why This Process Is Harder Than It Looks
- Missing the 3-year consulate deadline to sign the retention declaration, losing Spanish nationality without realizing it until years later.
- Assuming the “no dual nationality” rule works the same on both sides. It doesn’t: only Spain restricts it, the US doesn’t.
- Renewing a Spanish passport instead of formally signing the declaration, mistaking a working shortcut for legal protection.
- Ignoring US citizenship-based taxation after moving to Spain, and discovering the FBAR obligation only after a penalty notice.
- Letting residency permits lapse or spending too long outside Spain, which can reset the continuous residency clock needed for nationality by residence.
Living Between Two Countries? Sort Out Your Banking First
Whether you’re American and moving to Spain on a digital nomad or non-lucrative visa, or Spanish and settling in the US, holding two nationalities usually means managing money across two financial systems. Getting the right accounts in place before you relocate avoids delays with your first paycheck, your visa’s proof-of-funds requirement, or an expensive currency transfer.
Applying for the digital nomad visa or working remotely from Spain? bunq issues a European IBAN that works across the whole EU, so you’re not stuck opening (and waiting on) a local account before you can get paid or show proof of funds.
Freelancing or running a business while you sort out your residency? Qonto is built for freelancers and small business owners, with invoicing and multi-currency payments in one account.
Keeping ties to Spain while you’re based in the US? That matters if you’re working toward the 10-year residency mark for Spanish nationality. Bankinter’s fee-free digital account for new customers keeps your Spanish banking active without maintenance costs.
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Talk to a Lawyer Before You File
Whether you need to protect Spanish nationality after naturalizing as a US citizen, or you’re American and charting a path to Spanish nationality, the right move depends on details a generic guide can’t capture. At MigratioLex, we review your specific case, not a template. We respond within 24 hours, in English, French or Spanish.
Book Your Initial ConsultationThis article is for informational purposes only and does not constitute legal advice. It is based on Articles 22 and 24 of the Spanish Civil Code and general US citizenship-based tax rules as of publication; requirements can change, so confirm your specific situation with a qualified professional before acting on it.
