Meanwhile, more than half of Biden's balance came from "small-dollar donors" who gave $200 or less. And according to figures previously released by the campaign, most of that, $33 million, was raised in the first half of the month before financial markets plummeted and much of the country went into lockdown.
Biden's fundraising efforts have been hit by coronavirus-related restrictions, which have left the 77-year-old sheltering in his Delaware home and unable to travel and meet prospective donors.
He acknowledged that he probably will not keep up the fundraising pace in April.
"He has a lot more money than us, and we are facing an uphill battle trying to catch up now," he said in his note to supporters on Monday night.
And while Trump may be down in the latest approval ratings over his handling of the crisis, some Democrats are worried that his ubiquitous presence leading daily coronavirus press conferences is overshadowing Mr Biden.
Yet some in his team remains optimistic that he could still see a boon from recent endorsements from former president Barack Obama and Senator Sanders as voters rally behind the only man now able to prevent Mr Trump from winning a second term.
"This has been the best response I've ever had to any fundraising letter I've sent out [than] I have for 30, 40 years," said Bill Singer, a Democratic donor and member of Biden's national finance committee, of a coming virtual fundraiser aimed at Chicago-area donors.
"The people I'm talking to may have been for [Elizabeth] Warren, may have been for [Pete] Buttigieg, may have been for [Amy] Klobuchar or even [Kamala] Harris, but all that is behind them," he told The Washington Post.
"They're all saying, 'We're all in for Joe. He's the nominee. We have to beat Trump. We have to do it.' "
One remaining question is how much of his $60 billion fortune Mike Bloomberg, former New York Mayor, invests in the race. The newly released figures revealed that Bloomberg spent $1 billion on his own failed attempt at the Democratic nomination - the biggest self-funded campaign in US history.