Campaign aides told The New York Times of the near three-day fundraising total on Friday.
Biden campaign manager Jennifer O'Malley Dillon told other aides of the outpouring of donations on Wednesday, one day after Harris joined the Democratic ticket.
CNN reported that the campaign had raised $48 million by Thursday night, 48 hours after Biden named Harris.
By contrast, the Biden campaign had raised less than $61 million during all of 2019.
In their first appearance together on Wednesday, Biden and Harris criticized the Trump administration's handling of the COVID-19 pandemic and promised to lead a "comprehensive" response if they're elected.
Biden and Harris are scheduled to appear together Friday to sign official documents to accept the party's official nomination during the Democratic National Convention next week. The event was originally scheduled to be staged entirely in Milwaukee, but the pandemic persuaded the party to make it a virtual event.
The Democratic party this week unveiled the lineup for the convention. The first night, on Monday, will include addresses by former first lady Michelle Obama and former candidate and Vermont Sen. Bernie Sanders.
The second night will feature former President Bill Clinton and potential future first lady Jill Biden. The third night, Wednesday, will include speeches by Harris, 2016 Democratic nominee Hillary Clinton, Massachusetts Sen. Elizabeth Warren and former President Barack Obama.
Biden will accept the nomination on the final night, next Thursday, from his home in Delaware. Others who will speak on the final night include former candidates Pete Buttigieg and Cory Booker -- and Atlanta Mayor Keisha Lance Bottoms and Illinois Sen. Tammy Duckworth, who were both considered as Biden's vice presidential running mate.
The full schedule can be found on the Democratic National Convention website.