need help for travel with 2 nationalities / 2 passports

Your child will need to EXIT and ENTER Vietnam using ONLY the Vietnamese passport. Similarly your child will need to EXIT and ENTER France using ONLY the EU passport. That's the way it works for all multiple/dual citizens anywhere.

Outside of Vietnam or any of the EU countries your child can enter or exit using whatever passport is most advantageous (or convenient).

Cheers,
James     Expat-blog Experts Team

Thank you so much James for your help !

Not sure if this still is the case nowadays, but I also hold two citizenship's. On one occasion I needed consular help but when I went to the consulate they said that in a foreign country I am considered citizen of the country under which nationality I entered the country and you can only use one passport to travel.

However, in your case I’d use the VN passport to enter VN but take the French one along as well because when exiting again, they may ask where your EU/Schengen visa to enter France is. Then you can show them the French passport. But keep in mind, you or your child will not be considered French citizen while in VN if traveling with the VN passport. Perhaps check that with the french Embassy or consulate.

Hi snake77,

You may have misunderstood slightly what the Consulate was telling you.

Generally speaking when you naturalize as a citizen of any country, WHILE YOU ARE PHYSICALLY IN that country (or any of its territories) you are considered first and foremost to be a citizen of that country only.

That means that you cannot fall back on any other citizenship you may hold, while there. So for example, if you have a run-in with the law in a country in which you're a citizen (even naturalized), you cannot count on any consular assistance from your other country of citizenship. Their hands are tied, you aren't able to get anything from them in such situations.

And yes, if you're a citizen of any EU country you would need your EU passport, or permanent resident ID to travel to another EU country as far as I'm aware.

Cheers,
James