Trump shared his positive COVID-19 results just days after taking the debate stage with his Democratic rival.
The former vice president's wife, Dr. Jill Biden, has also tested negative.
[Ads /]
Earlier Friday, Biden sent his sympathies to the Trump family.
"Jill and I send our thoughts to President Trump and First Lady Melania Trump for a swift recovery. We will continue to pray for the health and safety of the president and his family," Biden tweeted.
Biden's running mate Kamala Harris was tested Thursday as part of the campaign's routine testing of principals and her results were negative, an aide told ABC News.
SEE ALSO: President Trump, first lady Melania test positive for coronavirus, say they are quarantining
Trump says he and first lady tested positive for coronavirus
Although socially distanced, Trump and Biden spent 90 minutes on stage together with no masks Tuesday for the first presidential debate at Case Western Reserve University and Cleveland Clinic in Cleveland, Ohio.
[Ads /]
They did not shake hands, but it is unclear if the candidates came into closer contact that night.
Biden has been repeatedly tested in the past few weeks, taking a very opposite approach from the president, who has spent much of the year downplaying the virus that has killed more than 205,000 Americans.
WATCH: Political analyst Laura Washington on Trump, first lady's positive COVID-19 tests
Political analyst Laura Washington discusses President Trump, First Lady Melania testing positive for COVID-19
The former vice president has held very few campaign events, all of which enforced very strict safety precautions, like social distancing. He also regularly wears a mask in public, something Trump mocked him for at Tuesday night's debate.
"I don't wear masks like him," Trump said of Biden. "Every time you see him, he's got a mask. He could be speaking 200 feet away from me, and he shows up with the biggest mask I've ever seen."
[Ads /]
Trump's family members, who were sitting in the audience, did not wear face coverings during the debate. Press observed that a Cleveland Clinic doctor unsuccessfully attempted to get Trump's guests to wear masks.
Throughout his campaign, Biden has aimed to underscore his message that the coronavirus remains a very serious threat to the United States.
MORE: Pres. Trump tested positive for coronavirus. How serious is his health risk?
President Trump has COVID-19. How serious is his risk?
The Associated Press contributed to this report.