Traveling With Two Passports: Which One to Use and When

Holding two passports gives you a choice at most borders, but not at all of them. The US, the UK and Canada each tell their own citizens which passport to use, and an airline can refuse boarding when the passport you show does not fit the trip. Below are those 3 rules, a passport-by-checkpoint table for 3 sample routes, and how dual nationals use ESTA.

Which passport to use at each checkpoint

Wherever you are a citizen, that country’s passport is the one to show, on the way in and, where its law says so, on the way out. Each passport carries its own expiry date, and a destination applies its minimum validity rule to the one you show there, not to the one in your bag.

Pick the passport for each leg of a trip

1. List every country on the route, including any where you only change planes.
2. Mark the countries where you are a citizen, and plan to enter each on its own passport.
3. Choose, for every other country, the passport that needs no visa, or an ETA instead of one.
4. Apply for any visa, ESTA or ETA on that same passport, never for a country where you are a citizen.
5. Book the ticket in the name exactly as printed in the passport you will show at check-in.
6. Pack both passports and check that each is valid for the legs it covers.

US dual citizens: enter and leave on the US passport

The US gives its citizens no choice. Section 215 of the Immigration and Nationality Act makes it illegal for a US citizen to enter or leave the United States on anything other than a US passport.

It applies at check-in abroad too: CBP’s ESTA FAQ expects US citizens who also hold a Visa Waiver Program nationality to use the US passport both departing the foreign country and arriving in the US. A US citizen child who has never had a US passport still cannot get a US visa, so get the child one before the first trip.

British dual citizens: UK passport or certificate of entitlement

Airlines enforce the UK’s rule at check-in, so it decides whether you board.

Since 25 February 2026 the UK has enforced its ETA scheme, and airlines block boarding for anyone without an ETA, an eVisa or other valid documentation. That catches British citizens who turn up with only a US, Canadian or French passport. All 3 are ETA nationalities, but a British citizen cannot get an ETA, so the airline needs the British passport or a certificate of entitlement. Certificates of entitlement have been issued digitally since 26 February 2026.

There are 2 exceptions. A carrier may accept an expired UK passport issued in 1989 or later together with a valid passport of an ETA nationality, if the personal details match, but that is the carrier’s decision. If you became British after settling under the EU Settlement Scheme, you can travel on your other passport or an EU, Norwegian, Icelandic, Liechtenstein or Swiss national ID card, once you have checked your eVisa.

Canadian dual citizens: the Canadian passport to fly home

Under Canada’s rule, a Canadian with dual citizenship needs a valid Canadian passport to return to Canada by air. It applies even when the country you fly from requires your other passport, and even when you are only passing through Canada. A special authorization may let you fly without one if you qualify, but plan around the passport.

Dual citizen travel examples: 3 round trips

The table applies those rules to 3 invented travelers. Each column is one round trip, and each row is a point where a passport comes out.

Checkpoint	US-Canadian, New York to Toronto	British-Canadian, Toronto to London	US-Mexican girl, 14, Chicago to Mexico City with her grandmother
Outbound check-in	Both: US passport to leave the US, Canadian passport to fly into Canada	British passport, since a British citizen cannot get an ETA	US passport, required to leave the US
Arrival	Canadian passport	British passport, or the Canadian one with a certificate of entitlement	Check with a Mexican consulate: a country may require its own passport or ID from its citizens
Return check-in	US passport, required to enter the US	Canadian passport, required to fly to Canada	US passport, plus notarized permission to leave Mexico without her parents
Arrival home	US passport	Canadian passport	US passport

The girl’s trip adds a document. Mexico requires Mexican minors, dual US citizens included, to carry notarized written permission from a parent or guardian when they travel without that parent or guardian. Her parents sign a consent letter for the trip and have it notarized before she flies. Without it, Mexican authorities have sometimes stopped US-citizen minors from leaving.

Using ESTA as a dual citizen

An ESTA approval belongs to one passport, and CBP says a dual citizen should use that passport to board the plane and to arrive in the US. If both your countries are in the Visa Waiver Program, CBP strongly recommends choosing one for US travel and using it every time, since 2 ESTA approvals for one person cause confusion and delays. The form also asks for your other citizenships and the most recent passport from each, even an expired one.

Travel on a passport from outside the program and you need a visa, not an ESTA. The State Department adds that a program national who also holds Cuban, Iranian, Iraqi, North Korean, Sudanese or Syrian nationality cannot use the program and applies for a visa. An approval lasts 2 years or until the passport expires, whichever comes first, so a new passport, whether it replaces an expired one or one that got damaged, needs a new ESTA and a new fee.

This is an invented sample. Claire Dubois, British and French, lives in Lyon. Both passports qualify for the program, so in November 2026 she puts her ESTA on the French one and lists her British citizenship on the form. In December 2026 she flies Paris to New York, then on to London.

• Paris check-in and US arrival: French passport, the one her ESTA is linked to.
• New York check-in for London: British passport, because she cannot get an ETA and the airline checks for UK permission.
• London arrival: British passport.

Her French passport expires in March 2027, which ends the ESTA too, so any US trip after that needs a new ESTA on the new passport.

Which passport to book your flight with

Book with the passport you will show at check-in and on arrival at your destination, in your name exactly as that passport prints it. For a domestic US flight either passport works: TSA accepts a foreign government-issued passport as ID at airport security.

Risks in your other country of citizenship

The US, the UK and Canada all allow dual citizenship, but your other country of citizenship may treat you as its own citizen only. The State Department lists what that can mean for Americans:

• You may need that country’s passport or ID to enter, and some countries require exit visas or impose exit bans.
• Local authorities may not recognize your US nationality, especially if you did not enter on the US passport, and may not notify the US embassy about you.
• You may face military service, and some countries prohibit dual nationality altogether.

A dual national gets no British diplomatic help in their other country of citizenship, so a British-French citizen in France cannot turn to the UK. Canada warns of different entry and exit rules, enhanced screening and refused consular access, and both governments advise asking that country’s embassy about its rules before you go.