With all the precincts reporting, Feinstein had 5.6 millon votes, or 61 percent, compared to 3.5 million votes, or 39 percent, for Emken.
Emken did not return a call from Patch for comment. Her campaign officials said earlier in the evening the candidate's voice was hoarse from her final days of campaigning.
Emken came in second in the June's open primary, earning her the right to face the incumbent senator in November.
Emken graduated from UCLA in 1984 with degrees in economics and political science. She worked in corporation operations and financial analysis at IBM.
Emken lives in Danville with her husband, Craig, their two daughters and their son Alex, who has been diagnosed with autism spectrum disorder. Emken has been a nationwide advocate for developmentally disabled children.
In 2010, Emken finished fourth in the Republican primary for the region's congressional seat.
Emken campaigned in Contra Costa County this morning and spent the afternoon in Orange County. She awaited election results this evening at campaign gathering in a hotel in Costa Mesa.
Feinstein, the former mayor of San Francisco, has been in the U.S. Senate since 1992. She was the first woman ever elected from California to the Senate.
During the past year, she has served as the chairwoman of the Senate Select Committee on Intelligence.
Patch will have up-to-the-minute results and reaction to this and other races after the polls close at 8 p.m.