Trump's fellow Republicans voted to approve the judge, overcoming the unified opposition of Democrats.
Barrett, 48, is expected to take the oath of office at the White House on Monday night.
Her appointment seals for the foreseeable future a 6-3 conservative majority on the top US judicial body.
Only one Republican - Senator Susan Collins, who faces a tough re-election battle in Maine - voted against the president's nominee in Monday evening's vote.
