Social Democrat Heinz Fischer, 65, was sworn in Thursday as Austria's new president, succeeding Thomas Klestil who died on Tuesday two days before he was due to leave office.
"I pledge to respect and protect the constitution and the law of my country and to carry out my duties to the best of my ability," Fischer said as he took the oath before both houses of parliament.
Fischer was elected to the largely ceremonial post on April 25 and is Austria's eighth president.
About 1,000 guests looked on as he was sworn in, among them former president Kurt Waldheim, who was plagued by accusations of his Nazi past, and Klestil's widow, Margot.
Klestil, a political conservative and former ambassador to the United Nations and Washington, succumbed to multiple organ failure late Tuesday after serving as president for two six-year terms. "I want to thank Thomas Klestil for his life's work and pay my deepest respect to his widow," Fischer, who was wearing a black suit and tie, said in his inaugural speech.
He is a career politician who was deputy parliamentary speaker when he was elected in April. Fischer is Austria's first socialist president since Rudolf Kirchschlaeger, who left office in 1986.