Mr Biden struggled to raise money during the Democratic primary, but ever since he became the apparent nominee last spring, money has poured into his campaign.
In July, he all but closed a huge cash-on-hand advantage enjoyed by President Donald Trump.
The massive August haul speaks to the enthusiasm among Democrats to oust Mr Trump from office.
Donald Trump is the greatest fundraising tool in the history of politics
The new flood of contributions, which came from grassroots supporters as well as deep-pocketed donors, should alleviate any lingering concern over whether Democrats will be able to flood the airwaves with advertising in key battleground states that will ultimately decide the outcome of the election.
“These numbers humble me,” Mr Biden wrote in a message to supporters.
“Even in a global recession, working families set aside some money to power this campaign, and a little bit added up in a big way.”
Mr Trump has yet to release his fundraising figures for the month of August.
After amassing a massive war chest over the past three years, the Trump campaign said recently that they were conserving money for after Labour Day.
Recently, they went mostly dark on the airwaves.
While they placed additional advertising this week, Mr Trump is still getting outspent by Mr Biden by nearly double, advertising data shows.
Democratic officials attribute the amount raised to antipathy towards Mr Trump, the selection of Senator Kamala Harris as Mr Biden’s vice presidential nominee and a successful convention that showcased Mr Biden’s empathy in contrast to Mr Trump.
“Donald Trump is the greatest fundraising tool in the history of politics,” said Democratic National Committee (DNC) finance chairman Chris Korge.
The money was raised in conjunction with the DNC.
While candidates face a 2,800 dollar (£2,100) limit per election, Mr Biden can raise far more than that through a joint fundraising committee with the DNC that allows him to collect individual cheques worth upward of 600,000 dollars (£450,000).
The money is split between his campaign, the DNC and state parties.
The haul also gives outside groups supporting Mr Biden’s campaign additional leeway to direct their money towards other efforts that could give Democrats an edge in what is expected to be a tight election, instead of just giving Mr Biden advertising air cover.
“Because Biden has been so successful raising money, it has allowed us to move resources into vote by mail and get out the vote programmes,” said Guy Cecil, chairman of Priorities USA, the largest Democratic super PAC.
