Speaking at a Manhattan fundraiser on Monday night, the Democratic candidate said he had received donations from 360,000 people with an average contribution of $55 – figures that suggest he has amassed $19.8m so far.
This eclipses the total of any of the other Democratic presidential candidates in the first quarter of the year.
Bernie Sanders reported taking in $18.2m from about 500,000 donors and another $2.5m in transfers from previous campaigns.
Mr Biden's fundraiser was hosted at the Upper East Side home of Jim Chanos, the president and founder of Kynikos Associates, a short-selling investment firm.
The former vice president told supporters at the event that their contributions have "allowed me to be able to compete in a way that I've never been able to before".
"We've raised a great deal of money," he said.
He added that supporters were vouching for him by writing him a check, "which is essentially saying: 'I respect this person. I think this person will do a good job'".
It is unclear whether the Biden campaign intended to release his figures publicly. Typically, campaigns wait until the close of the quarter to announce their fundraising tallies.
There are still 12 days left in the fundraising quarter, which ends on 30 June. The Federal Election Commission will make candidate filings public on 15 July.
The figures shared by Mr Biden on Monday night provide an early glimpse into his fundraising prowess since he entered the campaign on 25 April, which was past the first campaign fundraising disclosure deadline and later than many rivals.
Mr Biden's campaign announced it had raised $6.3m in the first 24 hours after he entered the race, the largest take among the candidates.
His efforts were boosted by a large fundraiser on the first day of the campaign, as well as Facebook ads that were targeted at generating first-day donations.
This is an important deadline that will provide an indication of which of the nearly two dozen candidates have risen to the top
Later on Monday night, another of Mr Biden's Democratic rivals, Elizabeth Warren wrote on Twitter: "I don't spend time at fancy fundraisers. Instead, I spend my time meeting voters and thanking grassroots donors who chip in what they can.
"Donate $3 to my campaign, and you might just get a call from me to thank you!"
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