Chuck Hagel has been sworn in as the nation's next defense secretary, according to the Associated Press.
He took the oath of office at the Defense Department, which is facing deep budget cuts.
Hagel was expected to address civilian and uniformed employees at the department later in the day Wednesday.
The Senate voted Tuesday to confirm Hagel. The vote was 58-41, with four Republicans joining Democrats in backing President Barack Obama's nominee.
Nebraska Senators Mike Johanns and Deb Fischer both took part in the vote. Senator Fischer voted against the confirmation, while Senator Johanns was one of four Republicans to vote for it.
The vote ended a contentious fight over the president's choice for his second-term national security team.
Republicans opposed the former two-term Republican senator from Nebraska, casting him as out of the mainstream and overly critical of Israel. But Democrats stood together for Hagel, a twice-wounded Vietnam combat veteran.
Hagel will succeed Defense Secretary Leon Panetta, who is stepping down after four years as CIA director and Pentagon chief.
The vote came just hours after Republicans dropped their delay and allowed the nomination to move forward. The Senate vote to end the filibuster was 71-27.