Nehammer's first act as chancellor was to conduct a Cabinet reshuffle, with predecessor Alexander Schallenberg returning as foreign minister.
ADVERTISEMENTKarl Nehammer has been sworn in as Austrian Chancellor at an official ceremony in Vienna.
The former interior minister replaces Alexander Schallenberg, who announced on Friday that he would step down from the role.
Nehammer was later chosen as the leader of the country's largest political group, the Austrian People's Party (ÖVP).
He is the third person to hold the role of chancellor in the last two months after Schallenberg and Sebastian Kurz.
Last week, Kurz said he would retire from politics amid corruption scandals and the birth of his first child.
The announcement prompted his successor Schallenberg to also resign, stating that he would make way for someone to take over as both the head of government and the leader of the ÖVP.
Nehammer was sworn into office on Monday in a televised ceremony at Vienna's Hofburg Palace by President Alexander Van der Bellen.
Speaking to reporters on Friday, Nehammer thanked Schallenberg and said "he was ready, in a very tough situation, to take responsibility for this country, and to serve this country".
The 49-year-old is seen by analysts as "loyal" to his conservative party and will "stabilise" the shaky coalition with the Austrian Greens.
Born in Vienna in 1972, Nehammer began his career in the military before moving to politics as a communications advisor. He was elected an ÖVP lawmaker in 2017 and joined the government in January 2020.
During his time as Interior Minister, Nehammer had to deal with Austria's first-ever jihadist attack in November 2020, which killed four people and injured 23 others.
The interior ministry was strongly criticised for having failed to monitor the attacker, even though they had been alerted to the danger.
As chancellor, Nehammer will be tasked with guiding Austria out of COVID-19 restrictions. The Alpine country was the first EU member state to impose confinement measures on non-vaccinated citizens and will make coronavirus jabs mandatory from February.
Nehammer has also been criticised by NGOs for his strong stance on immigration and asylum-seekers.
His first act as chancellor has been to conduct a Cabinet reshuffle, appointing new finance, interior, and education ministers.
Schallenberg meanwhile has returned to his former post of Austrian foreign minister in a cabinet reshuffle.