Chief Justice John Roberts administered the Judicial Oath to Barrett, officially making her the court's 103rd associate justice.
"Upon administration of that oath, she will be able to begin to participate in the work of the Court," the Supreme Court said in a press release prior to the ceremony, adding that a "formal investiture ceremony will take place at a special sitting of the Court in the Courtroom at a later date."
The ceremony took place at 10 a.m. with all of the justices participating, although Justice Stephen Breyer attended virtually, according to Supreme Court public information officer Kathy Arberg. Retired Justice Anthony Kennedy was in attendance, as were the wives of Justices Clarence Thomas and Brett Kavanaugh.
The new justice was sworn in on a family Bible that her husband Jesse Barrett held. Their children were not present.
Barrett's confirmation process quickly took place following her nomination. After the Senate Judiciary Committee held a hearing and voted Thursday to advance her nomination to the Senate floor, Senate Republicans swiftly voted Sunday to limit debate on the matter before holding a confirmation vote Monday evening.
Following a 52-48 vote, Barrett then went before Justice Clarence Thomas to take her constitutional oath at a White House ceremony.
Barrett now will be able to sit with the other eight justices to rule on cases that include several high-profile issues. Republicans have requested that the Supreme Court speedily decide a case involving changes to Pennsylvania's election laws, after the court previously left in place a lower court decision that extended the deadline for ballots to be received for November's election.
One week after the election, the Supreme Court will hear oral arguments in a case where the fate of the Affordable Care Act could be decided. Democrats accused Republicans of rushing Barrett through her confirmation process so she could rule against the ACA, as she had previously criticized the 2012 decision that upheld it.
Barrett noted during her confirmation hearing that the issues involved in the current case are different from the 2012 one, and that she has not indicated which way she might lean in the new matter.
Fox News' Shannon Bream and Bill Mears contributed to this report.