He will take his seat on Tuesday - on the far right of the bench, next to Justice Elena Kagan - hearing immigration and other cases.
The other eight justices are all in attendance for Monday's swearing-in, which is entirely ceremonial.
Police office guards the main entrance to the Supreme Court in Washington, Tuesday, Oct. 9, 2018. There were no disruptions by protesters during the oral arguments, with security tight in the courtroom.
As the newest member of the court, Kavanaugh will take on a few special jobs.
Kavanaugh, a veteran of such proceedings after 12 years on an influential US appeals court, looked at ease as he asked several questions during two hours of lively oral arguments involving a federal sentencing law for repeat offenders. "The justices do not sit on opposite sides of an aisle". Justice Sonia Sotomayor even appeared to playfully pinch Gorsuch's arm as she asked a question about the kind of physical force necessary to have a crime be treated as violent under a federal enhanced sentencing law. In this case, the issue turned on whether a Florida robbery statute would call for an enhanced sentence.
He went on to thank President Trump for his unwavering support and cited Kennedy, for whom Kavanaugh clerked, as a role model and mentor. Conservative Justice Neil Gorsuch joined the court past year.
According to Deadline, Kimmel joked that Trump is "flying extra high today after the confirmation of beer-battered Brett Kavanaugh, who is now on the United States Supreme Court despite all of the stuff you know about".
Protesters held signs that said, "We will not forget" and "We do not consent", following the acrimonious fight that culminated in Kavanaugh's 50-48 confirmation by the Senate.
Judge Kavanaugh was accused of sexually assaulting women three decades ago, accusations that saw the confirmation process deteriorate into a bitter partisan battle.
Kavanaugh denied the allegations and during a Senate hearing on September 27 accused Democrats of an "orchestrated political hit".
He later wrote in a newspaper opinion piece that he regretted some of his comments.
The two-vote margin of victory in the Senate made it the closest Supreme Court confirmation vote since 1881 - and by far the most contentious since Clarence Thomas in 1991.
His first day on the bench is Tuesday when he and his colleagues will hear arguments about longer jail terms for repeat offenders.
Before the arguments began, Chief Judge John Roberts welcomed Kavanaugh to the court. Throughout his exceptionally turbulent confirmation process, Kavanaugh touted his long history of empowering women in the workplace, pointing out how he's actually practiced what so many others preach.
"Those who step forward to serve our country deserve a fair and dignified evaluation, not a campaign of political and personal destruction based on lies and deception", he said.
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