"You, sir, under historic scrutiny, were proven innocent", Trump said to Kavanaugh. "Every litigant at the Supreme Court can be assured that I will listen to their argument with respect and an open mind", the newly minted Justice added.
The ceremony was attended by Kavanaugh's family members, other judges of the Supreme Court, top Senators, members of the Trump administration and a battery of reporters.
The result is a tacit endorsement of Kavanaugh's ruling on the limit of executive power in agency law, one that sets a precedent for future court cases unless the Supreme Court chooses to revisit it.
The bruising campaign to install Kavanaugh onto the court could leave a mark on his reputation and on public confidence in the institution, legal experts say.
"It was a disgraceful situation brought about by people that are evil", he said.
The president's rendering of a verdict on the sexual assault allegations risks further antagonizing political opponents at a moment that the "Me Too" movement demands accountability for sexual misconduct.
One guy's a college sports fanatic who loves beer and football, the other is an average guy from Kentucky who saw his twitter mobbed with interest in recent weeks, prompting him to declare "this is a awful time to be named Brett Kavanagh". Americans opposed his confirmation 51 percent to 41 percent, according to a CNN poll conducted October 4-7.
His path to confirmation was turbulent - opposition to him intensified after Christine Blasey Ford accused him of sexually assaulting her decades ago, when they were teenagers.
Sulawesi quake: Last-ditch search for survivors as Indonesia disaster toll tops 1500
By Thursday, the official death toll stood at 1,424, but it will certainly rise as the bodies were still being recovered in Palu . Bank Indonesia was helping restore payment systems and some cash machines were working again in Palu as banks re-opened, he said.
After an extra Federal Bureau of Investigation probe - which media reports say was drastically curtailed by the White House - also found nothing new, Kavanaugh was finally voted into the coveted post.
Other major polls reflected similar sentiment.
The FBI took another look at Kavanaugh's background and did not find corroboration to support the claim, which led to his confirmation by a 50-48 vote.
The new justice dived into his new job, asking a handful of questions in the first arguments of the day following a traditional welcome from Chief Justice John Roberts, who wished Kavanaugh "a long and happy career in our common calling".
The other eight justices were all in attendance.
Supreme Court Associate Justice Brett Kavanaugh (L) hugs his wife Ashley after the ceremony.
"For as long as Kavanaugh sits on the court, he will remain a symbol of partisan anger, a haunting reminder that behind the smiling face of judicial benevolence lies the force of an urgent will to power", Yale law professor Robert Post wrote in Politico.
The Washington Examiner noted Rep. Jerrold Nadler, D-N.Y., has indicated the House Judiciary Committee might investigate Kavanaugh if his party retakes the majority in November and he becomes the panel's chairman.
In an interview with Fox News Channel's Martha MacCallum, Grassley was asked whether he believes the Senate should take up a hypothetical Supreme Court nomination during 2020, when President Trump will be up for reelection.