BERLIN — A new coalition government was sworn in on Monday in Austria, and for the first time in more than 10 years it includes the far-right Freedom Party, a watershed for the populist movements that unsettled European politics this year.

The return to power of the Freedom Party, which was founded by neo-Nazis after World War II, was concerning enough that Austria’s president, Alexander Van der Bellen, took the exceptional step of eliciting several promises from the new government before he would administer the oath of office.

Those included acknowledging Austria’s commitment to European Union and its responsibility to a Nazi past that tore apart the Continent last century.

Mr. Van de Bellen also reminded the new government leaders that they represent everyone in Austria, a rejoinder to a campaign characterized in large part by an antipathy toward immigrants.