The 70-year-old Biden took the oath of office from Supreme Court Justice Sonia Sotamayor during a private ceremony Sunday at the U.S. Naval Observatory, the vice president's residence.
Biden and President Barack Obama will take the oath of office again on Monday during a public ceremony at the Capitol.
Here is the oath of office taken by Joe Biden on Sunday as he begins his second term as vice president:
I, Joseph R. Biden Jr., do solemnly swear that I will support and defend the Constitution of the United States against all enemies foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God.