Effective September 2015 – Danish law allows for dual citizenship
Danish Nationals living in the United States now enjoy the option of having dual citizenship.
This means that Danes can apply to become US citizens via naturalization in the USA without losing their Danish citizenship. The Application for Naturalization, form N-400 is available here: https://www.uscis.gov/n-400
Danes who lost their Danish citizenship when they became citizens of another country prior to September 1, 2015, can apply to have their Danish citizenship reinstated. For more information about Citizenship [in Danish statsborgerskab og indfødsret] please see www.statsforvaltningen.dk and http://www.statsforvaltningen.dk/site.aspx?p=8903 .
The application, Erklæring om Generhvervelse af Dansk Indfødsret for Tidligere Danske Statsborgere, is available here http://www.statsforvaltningen.dk/sfdocs/Andre%20omr%C3%A5der/Indf%C3%B8dsret/20150901/Erkl%C3%A6ringsskema%20-%20dobbelt%20stb%20%C2%A7%203.pdf
Questions about the application should be directed to the State Administration at phone no.: 011 45 72 56 70 00 or via e-mail: email@example.com