More specifically, you are allowed to keep your previous citizenship if any of the following apply: 1) Your previous citizenship is in an EU member state or in

More specifically, you are allowed to keep your previous citizenship if any of the following apply: 1) Your previous citizenship is in an EU member state or in Switzerland. 2) Your previous citizenship is in a country which has no process for renouncing citizenship, or where renouncing citizenship is illegal or otherwise dangerous or unnecessarily difficult (there is a published list of countries where that is the case, and having citizenship of one of those automatically removes the renunciation requirement for that country's citizenship) 3) You make a case to the government that renouncing your previous citizenship is an undue hardship, with costs, risks, or impact on your life that are beyond reasonable (these are decided on a case by case basis) Incidentally, I'm intimately familiar with the naturalization process. If my knowledge can help anyone else, I'm happy to do so. Email/IRC contact in my profile.