She made the announcement in a video posted to Twitter on Thursday. The move comes as former Vice President Joe Biden consolidates support in the party and builds a massive delegate lead over his only remaining rival in the primary race, Sen. Bernie Sanders.
Gabbard, in the video, offered her "full support" to Biden.
But Gabbard also praised Sanders.
Gabbard, who backed the populist senator's 2016 White House bid, said: "I have great appreciation for Senator Sanders' love for our country and the American people and his sincere desire to improve the lives of all Americans."
Gabbard – a four-term congresswoman who in 2012 became the first Hindu elected to Congress – launched her presidential campaign in January of last year.
The Hawaii National Guard officer who served in the Iraq War advocated for a foreign policy that stressed that the U.S. stay out of overseas conflicts and entanglements.
But Gabbard was repeatedly criticized for her January 2017 trip to Syria – where she met with Syrian leader Bashar al-Assad and toured the city of Aleppo after it had been blasted to rubble by Assad’s regime.
Gabbard’s anti-intervention stance was blasted by 2016 Democratic presidential nominee Hillary Clinton – who referred to the congresswoman as “the favorite of the Russians” and suggested Gabbard was being groomed as a third-party candidate for the general election.
Gabbard, saying she was defamed by Clinton, sued her in January for $100 million. Clinton has moved to dismiss the lawsuit.
The 38-year candidate – who was the second youngest contender in the race after former South Bend, Indiana Mayor Pete Buttigieg – also had to apologize early in her campaign for past anti-gay comments and actions. A decade and a half earlier, she actively promoted “traditional marriage” and several times referred to LGBTQ activists as “homosexual extremists.”
Gabbard also repeatedly clashed with the Democratic National Committee over their presidential nomination debate criteria – which prevented the congresswoman and many of her rivals from making the stage.
Earlier this month she was one of the first in Congress to push for universal basic income payments – made popular by former 2020 rival Andrew Yang – as a way to provide instant relief to Americans affected by the massive economic downturn caused by the coronavirus outbreak.
Gabbard, who's said she won't run for re-election to her House seat, embraced the concept of universal basic income last year. In an apparent effort to try and attract Yang supporters, Gabbard said hours after Yang ended his bid in February that she would continue “to carry the torch” for his Freedom Dividend.
The candidate spent much of her time early this year campaigning in New Hampshire – which holds the first primary in the White House race and votes second in the nominating calendar, after Iowa. Gabbard even rented a home in the state. But she finished a disappointing seventh place in the primary, winning only 3 percent of the vote.
She barely registered in the Nevada caucuses and won just 1 percent of the vote in the South Carolina primary and in many of the Super Tuesday contests. But Gabbard stayed in the race – even after every candidate other than Biden and Sanders dropped out.
In the contests the past two weeks, Gabbard often won fewer votes than candidates who had already departed the race. In Tuesday’s primary in Florida, the congresswoman grabbed less than 1 percent of the vote, finishing behind former candidates Mike Bloomberg, Buttigieg, and Sens. Elizabeth Warren of Massachusetts and Amy Klobuchar of Minnesota.
She won just two delegates in the nomination race – both coming from her native American Samoa.
Fox News' Tyler Olson contributed to this report