The two held private swearing-in ceremonies at the White House and U.S. Naval Observatory, but will hold a ceremonial swearing-in on the steps of the U.S. Capitol on Monday. The Constitution requires that the president take the oath of the office on Jan. 20 before noon.
Obama took the oath of office with his hand on the family Bible, which was held by the first lady, Michelle Obama. The family Bible belonged to the first lady's family and dates to 1958.
"I did it," Obama said after delivering his oath.
Biden went first this morning. About 120 friends and guests showed up for the private swearing-in ceremony at the vice president's residence on the grounds of the U.S. Naval Observatory. Before the swearing-in, Biden, a Catholic, celebrated Mass. Biden was surrounded by his wife, children and grandchildren for the swearing in. Among the guests were several lawmakers, Democratic operatives and current and former administration officials.
Biden thanked his family, colleagues and friends for sharing the day with him. He then met up with President Obama to lay a wreath at the Tomb of the Unknown Soldier at Arlington National Cemetery.
"I am honored," Biden told his guests said after he recited the oath of office.
The president will took his oath before a few family and friends and handful of reporters in the Blue Room, which was the site of the only presidential wedding in the White House, when President Grover Cleveland married Frances Folsom in 1886.
Biden picked Justice Sonia Sotomayor for the honor. She became the first Hispanic and fourth female judge to administer an oath of office.
"It's an incredible honor to have Associate Justice Sonia Sotomayor swear me in," Biden said. "I believed strongly that she would make a great justice, and it was one of the greatest pleasures of my career to be involved in her selection to the court. From the first time I met her, I was impressed by Justice Sotomayor's commitment to justice and opportunity for all Americans, and she continues to exemplify those values today. Above all, I'm happy for the chance to be sworn in by a friend - and someone I know will continue to do great things."
Three women have previously sworn in presidents and vice presidents: Judge Sarah T. Hughes swore in President Johnson in 1963; Justice Sandra Day O'Connor swore in Vice President Dan Quayle in 1989; and Justice Ruth Bader Ginsburg swore in Vice President Al Gore in 1997, according to the White House.
Biden used his family Bible for today's ceremony, a 5-inch-thick tome featuring a Celtic cross on the cover. It has been in the Biden family since 1893. He used it each time he was sworn in as a senator and when he was sworn in as vice president in 2009. His son Beau used it when he was sworn in as Delaware's attorney general.
Obama is the seventh president or president-elect to have Inauguration Day fall on a Sunday, and is following the path of predecessors who held a private oath-taking on the constitutionally prescribed Jan. 20 date.
Meanwhile, the Obama campaign hosted a "legacy conference" with supporters and campaign volunteers in Washington today to discuss the future about the campaign operation they've built. The president's campaign built an impressive online and data operation. On the agenda are conversations about organizing, the budget crisis and gun violence among other issues.
This morning, Obama and his family attended services at the historic Metropolitan African Methodist Episcopal Church. In his sermon, the Rev. Ronald Braxton gave a nod to Obama's reelection effort. His sermon ended with a rousing call-and-response in which the congregants repeated "forward," a theme the president and his team used on the campaign trail.
With his swearing-in, Obama will officially begin his second term, but the president will deliver his big speech on Monday during the inaugural festivities.
White House senior adviser David Plouffe told Fox News that Obama's inaugural address will be more thematic and offer a call for national unity, while he will use the State of Union to spotlight the details of his second-term political agenda.
But Plouffe said the president's speech will emphasize one point "very strongly."
"People here in Washington need to seek common ground," Plouffe said.