In a video posted to Twitter, Harris said she has decided “with great enthusiasm” to endorse Biden’s presidential bid.
“I believe in Joe. I really believe in him, and I have known him for a long time,” she said.
“One of the things that we need right now is we need a leader who really does care about the people and who can therefore unify the people,” Harris said in the statement. “And I believe Joe can do that.”
Harris said she is supporting Biden because he is a man who has “lived his life with great dignity.”
“He is a public servant who has always worked for the best of who we are as a nation and we need that right now,” she said.
In the tweet accompanying the video, Harris said she will “do everything in my power to help elect him the next President of the United States.”
Moments after the video was posted, Biden posted a tweet of his own, thanking Harris.
“Kamala — You’ve spent your whole career fighting for folks who’ve been written off and left behind — and no small part of that alongside Beau,” he wrote, referring to his son who died of brain cancer in 2015.
“From our family: thank you.”
Harris, had also thrown her hat in the running to become the Democratic candidate, but dropped out in early December.
Other former Democratic candidates Amy Klobuchar, Mike Bloomberg and Pete Buttigieg have also endorsed Biden.
Harris’ endorsements comes before the next round of primaries, with six states voting Tuesday, including Michigan.
-With a file from The Associated Press