Everyone who had lived in one of the referendum regions since 1900 was entitled to vote, and more than 90% of the electorate turned out for the ballot.

In Zone 1 (North Schleswig), the people voted on 10 February 1920 en bloc, i.e. the result for the entire region was decided by simple majority. A total of 75,431 votes were cast for alignment with Denmark and 25,329 for becoming part of Germany. The majority of voters in the towns of Sønderborg, Aabenraa and Tønder, and in the parishes of Højer, Ubjerg and Tinglev actually voted for Germany, but the decision was made by the population of the region as a whole. In Zone 2 (Flensburg and Central Schleswig), the referendum was held on 14 March, when 51,724 votes were cast for alignment with Germany and 12,800 for incorporation into Denmark. In Flensburg, 75.2% of the voters opted for Germany, and a Danish majority was only recorded in two villages on the island of Før.

As a result of the referendums, the Danish – German border was moved approximately 70 km south and North Schleswig was gradually assimilated into Denmark over the period from 5 May through 10 July 1920. With this division of Schleswig, the right of self-determination was applied in practice, although it did not produce a clear ‘nationality border’. National minorities were to be found both north and south of the new geographical border – as is still the case to this day.