“I know Joe. He has lived his life guided by values and principles that mirror ones that most Americans can recognize,” the former first lady tweeted on Tuesday morning.
“He understands the struggles of everyday folks. Vote today for the future you want to see for our country. Vote for @JoeBiden.”
Ms Obama has passionately urged Americans not to vote for Mr Trump and instead lend their support to Mr Biden on choice occasions during this year's election cycle.
At the beginning of October Ms Obama released a blistering attack against President Donald Trump in her “closing argument” ahead of the presidential election.
In a rare political attack Ms Obama said that the United States has descended into “chaos” with a president who “isn’t up for the job”.
“Let me be as honest and clear as I possibly can: Donald Trump is the wrong president for our country," she said.
"He has had more than enough time to prove that he can do the job but he is clearly in over his head. He cannot meet this moment. He simply cannot be who we need him to be for us.”
She urged that American’s had a chance to elect a leader with “character and experience to put an end to this chaos,” and named Mr Biden as that choice.
During a virtual speech at the Democratic National Convention, the 56-year-old echoed similar sentiments, accusing the president of "faking" his way through the job and stoking racial tensions.
"Donald Trump is the wrong president for our country," she said. "He is in over his head. He cannot meet the moment. ... It is what it is."
Her husband and former president, Barack Obama, has also voiced his support for his former running mate, having recently appeared on the campaign trail to support Mr Biden in battleground states.
“Trump cares about feeding his ego. Joe cares about keeping you and your family safe,” Mr Obama said in Flint, Michigan on Saturday.
He added: “The president wants to get credit for the economy he inherited and zero blame for the pandemic he ignored."
Polling places are now open across the US in all states as voters continue to cast their ballots in the November 3 elections.
More than 100 million Americans had already cast their ballots ahead of election day according to the US Elections Project, a database compiled by Michael McDonald, a professor at the University of Florida.
With election day unfolding RealClear Politics National polling average has Mr Biden leading Mr Trump by 7.2 percentage points.
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