"I learned a long time ago that Hillary Clinton is a fighter and that's what we need in our next president," Clyburn, the highest-ranking African-American in Congress, said at Allen University in Columbia.
"I want to do everything I can to help Hillary Clinton crack the ultimate glass ceiling," he added.
Clyburn said he had worked with both Clinton and her primary opponent Bernie Sanders and that both were "pleasant and enjoyable."
"Hillary Clinton is far and away the best choice to reform our criminal justice system and restore the Voting Rights Act to its rightful place," he said.
And Clinton's foreign policy experience is one of the things that gives her an edge over Sanders.
"The best way to be prepared for foreign affairs in this country is secretary of state," Clyburn said. "So she has the experiences I think that will serve her well."
Clyburn acknowledged that there were college students in the crowd and addressed the fact that Clinton is not polling as well as Sanders with millennial voters.
"I'm for Hillary. I think Hillary's the best choice. But whoever you are for, you go out. You work for that candidate. And you vote," he said. "I don't have any problem with anybody who is out working for Bernie Sanders."
In a statement, Clinton said she was "incredibly honored" to have Clyburn's support, calling him "a lifelong progressive champion of affordable health care, educational opportunity and civil rights."
"I look forward to working with him to fight for universal health care, make college affordable, protect the environment, end red-lining in housing once and for all, make it easier to start and grow small businesses, expand his innovative "10-20-30" approach to invest in underserved communities and break the cycle of intergenerational poverty, and find every way we can to help families get ahead and stay ahead," she added.
Clinton has focused in recent weeks on casting herself as the logical successor to Obama, saying she'd defend the President's legacy. Sanders, meanwhile, has increasingly split with Obama as he has focused his message on economic inequality.
Speaking with CNN's Jake Tapper Friday on "The Lead," Clyburn swatted away a claim from Sanders
that Clinton was hugging President Barack Obama closely in order to win over the black community, pointing instead to Clinton's long history of advocating for black voters and the disadvantaged.
"Those are the kind of programs and priorities that are important to the African-American community," Clyburn said.
Clyburn's support comes the day before Nevada's Democratic caucuses -- the first test of whether Clinton's organizational strength and advantages among minority voters can withstand a challenge from Vermont Sen. Bernie Sanders.
It's likely to be most helpful, though, when the race shifts to South Carolina, which holds its Democratic primary on February 27. The state's heavy African-American population has helped Clinton build a massive lead there, and a big win could slow Sanders' momentum.