People greeted the VP as he praised San Jose Congressman Mike Honda during a campaign-style photo op at Hobee's Restaurant.
Honda faces a re-election challenge from Silicon Valley attorney Ro Khanna.
Biden was a clear crowd pleaser, but eventually had to leave the restaurant to attend a special event.
"My niece, Casey Owens, is graduating from Stanford," Biden said. "Getting her master's degree today and I'm heading over there right now so it's going to be a good day."
Biden returns to Washington Sunday.
He came to the Bay Area to attend Friday night's Democratic Party fundraiser in San Francisco.