Thousands of protesters demonstrated in the center of Vienna against the new Austrian coalition government of conservatives and far right, during his oath.
Among the posters were those that said "Do not let the Nazis rule".
The Freedom Party (FPÖ), the junior partner, is the only extreme right wing party that gains power in the EU.
The FPÖ and the People's Party (ÖVP) plan to implement stricter rules for asylum seekers, after the immigration concern for Austrian voters.
The coalition says that Austria will remain in the EU. The new chancellor is Sebastian Kurz, 31
There was a strong police presence on the outskirts of the Hofburg Palace during the oath.
Some 6,000 people demonstrated against the new coalition, reports Bethany Bell of the BBC.
The FPÖ was founded by ex-Nazis in the 1950s, but today denies any connection with the Nazi ideology.
The FPÖ has received some key positions in the coalition, has taken over the interior and defense, and been allowed to elect the new foreign minister.
The FPÖ has a cooperation agreement with the ruling Russian United Russia party President Vladimir Putin and the FPÖ say they want EU sanctions on Russia to be reduced.
The new Minister of Foreign Affairs, Karin Kneissl, is an expert in the Middle East who speaks Arabic and Hebrew.
Accuses German Chancellor Angela Merkel of "negligence" by allowing a record number of immigrants.
Controversially, he also said that the confusion in the Arab world was partly caused by unemployed youth "who can not find a woman today" because of their low status.
Hard in asylum
The coalition plans to have asylum seekers deliver all the cash they have when they submit an asylum application, so that their welfare is financed.
They will also have to turn over their mobile phones so that the authorities can s That is, from their data how they arrived in Austria and with whom they were contacted. Telephones will not be confiscated, but there will be systematic checks.
The FPÖ was in a coalition government before, in 2000. At that time there was a big protest and the government was diplomatically isolated in the EU. But this time the reaction has been much more moderate.
In 2015, Austria was at the center of the EU migration crisis, when more than one million asylum-seekers arrived in the hope of reaching Germany. The majority moved to Germany, but the Austrian resources stretched severely and the crisis fueled the anti-immigration sentiment.
Many were refugees from the wars in Syria, Iraq and Afghanistan.
In the third quarter of this year, asylum applications in Austria were approximately 25% lower than in the same period of 2016, reports Eurostat. In Germany, the figures were more than 75% lower.
According to the new plans of the Austrian government:
- Basic care will be provided to migrants in kind, no longer in cash benefits
- Doctors who provide basic medical care to migrants may have to provide more information than in the past, since "your duty of confidentiality will be limited," says the coalition program (in German)
- Spouses will be excluded from Austria in cases of polygamy, forced marriage or child marriage
- Asylum-seeking children will have to attend special "liaison" classes in shelters for immigrants, separated from general education. The coalition does not explain how that system will work. Many hostels are located in small cities and lack resources for such classes, reports the Austrian newspaper Der Standard.
In a post on Facebook, the leader of the FPÖ, Heinz-Christian Strache, said (in German): "It will no longer be possible for immigrants who have not worked here for a single day and have not paid anything in the system get thousands of euros in Social Security! " He added: "At this point, in the Freedom Party we have attached ourselves to a central electoral promise!"
The Danish government was widely criticized in Europe when it introduced similar measures.
Who is who in the new government?  Chancellor: Sebastian Kurz, ÖVP. The 31-year-old man was Foreign Minister in the outgoing government of Austria.
Minister of the Interior: Herbert Kickl, FPÖ. The party's general secretary and campaign director, 49, was a speechwriter for the late party leader Jörg Haider and an intimate confidant of Strache.
Minister of Foreign Affairs: Karin Kneissl, nominated by the FPÖ but not a member. The former diplomat, 52, speaks eight languages and is not afraid of the controversy.
A note on terminology: The BBC uses the term migrant to refer to all persons still moving to complete the legal process of claiming asylum This group includes persons They flee from countries devastated by war like Syria, to whom they are granted refugee status, as well as to people seeking work and a better life, and who governments will probably decide they are economic immigrants.