Biden presided over a ceremonial swearing-in for new Housing and Urban Development Secretary Julian Castro. He's the former San Antonio mayor whose political profile received a major boost in 2012 when President Barack Obama chose him to speak at the Democratic National Convention.
Castro's name has caught fire as a potential vice presidential nominee in 2016. Biden hasn't ruled out running for president that year.
Castro's wife held a Bible and his daughter stood nearby as he recited the oath.
Last month, Obama lavished praise on Castro during an unusual visit to HUD headquarters to welcome Castro to the job.