Vice President Joe Biden administered the oath to Clinton in a ceremonial star-studded gathering at the State Department, with actor Chevy Chase and designer Oscar de la Renta among those on hand.
"It is an overwhelming honor … to assume this position," Clinton said. "We have a lot of work to do (to ensure that) America's future can be even brighter than our storied past."
"In selecting Sen. Clinton for this critical task, I think the president selected a person of unrivaled talent and experience," Biden said. She is "equally at ease in the great diplomatic halls of Europe as she is in the small villages in Africa."
Several of Clinton's predecessors were in attendance for the unusual gathering, including Madeleine Albright, Lawrence Eagleburger, James Baker and Henry Kissinger. House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid also attended, as did Clinton's husband, former President Bill Clinton, and former first daughter Chelsea Clinton.
Hillary Clinton's official swearing-in took place January 21 in her former Senate office. The low-key event was attended only by her husband and Senate staff.
The Senate approved Clinton's nomination January 21 on a 94-2 vote, with only South Carolina Republican Sen. Jim DeMint and Louisiana Republican Sen. David Vitter voting no.
Some GOP senators suggested during Clinton's confirmation process that she had not done enough to resolve potential conflicts of interest arising from various fundraising activities tied to her husband.