Kagan is joining President Barack Obama at the White House on Friday for a ceremony to mark her confirmation as the nation's 112th justice. On Saturday, she's to be sworn in at the Supreme Court as the successor to retired Justice John Paul Stevens.
The 50-year-old U.S. solicitor general, who won confirmation Thursday over Republican opposition, will be sworn in twice by Chief Justice John Roberts.
She will recite one oath as prescribed by the Constitution in a private ceremony in the high court's Justices' Conference Room, with only her family present. Then, Roberts will administer a second oath, taken by judges, with the Kagan's family and friends and reporters present.
She won't be formally installed as a justice until Oct. 1 in a courtroom ceremony at the start of the court's new term.
Kagan isn't expected to alter the ideological balance of the court, where Stevens was considered a leader of the liberal wing. But the two parties clashed over her nomination and the court itself. Republicans argued that Kagan was a politically motivated activist who would be unable to put aside her personal opinions and rule impartially. Democrats defended her as a highly qualified trailblazer for women who could bring a note of moderation and real-world experience to a polarized court they said was dominated by just the kind of activists the GOP denounced.
Kagan is the first Supreme Court nominee in nearly 40 years with no experience as a judge, and her addition will mark the first time that three women will serve on the nine-member court together.
Obama hailed the addition of another woman to the court -- just a year after his first nominee, Justice Sonia Sotomayor, was confirmed -- as a sign of progress for the country. And he called the 63-37 confirmation vote "an affirmation of (Kagan's) character and her temperament, her open-mindedness and evenhandedness, her determination to hear all sides of every story and consider all possible arguments."
In the final tally, five Republicans joined all but one Democrat to support Kagan, giving her a slightly narrower margin of support than Sotomayor received.
GOP senators and conservative groups, including the National Rifle Association, argued that Democrats from conservative states should oppose Kagan because of her stances on social issues, including support for gun control measures and abortion rights.
But only one, Democratic Sen. Ben Nelson of Nebraska, voted "no."