"In the end, we could not overcome the registration advantage that Democrats have, and in particular in L.A. County," she said.
With 100 percent of precincts reporting, Boxer had 51 percent of the vote, while Fiorina received 42 percent of the vote.
When Boxer returns to Washington D.C., it will look different as many new Republicans move into the Senate and House of Representatives.
"I've been around a while," Boxer told Eyewitness News after her speech. "I've been in the minority, I've been in the majority, I've been in the small minority, the big minority, so you just do what's best for the people." Boxer said this was her toughest campaign.
Fiorina was a formidable opponent, hitting Boxer on hot-button issues that sparked Republican rage across the country. She stumped against Boxer's liberal politics, blaming Boxer and Democrats for failed economic policies, hammering away on the cost of the $814 billion economic stimulus legislation.
Because Boxer seemed vulnerable, the GOP poured millions into the race, believing that disgust over the economy would turn the tide in California.
According to the early exit polls, Boxer was ahead with a comfortable margin, but as votes were counted, her lead narrowed substantially, and Fiorina decided she was not going to concede just yet.
But Boxer held on, helped in good measure by the fact that Democrats outnumber Republicans by 2.2 million in the state.
Boxer, who voted by absentee ballot a few weeks ago, delivered a victory speech at about 11:20 p.m. in Hollywood. She declared the race was her 11th straight victory, "and what a sweet one it was."
"Everyone who's willing to work to make life better for the American people, whether they're an R or a D or an independent, I'm ready to work with them," Boxer said after her victory speech.
The economy and the scramble for jobs defined the dialogue for this campaign. Boxer's mantra was that Fiorina represented a return to Republican policies of the past, and that those policies had created the recession. She painted Fiorina as out-of-step with California voters on the issues of abortion and gun control.