The US president and First Lady Melania Trump both tested positive for the infection on Thursday just weeks before the November 3 election.
Mr Trump tweeted: “Tonight, @FLOTUS and I tested positive for COVID-19. We will begin our quarantine and recovery process immediately. We will get through this TOGETHER!”
He is now expected to be in quarantine for two weeks while facing treatment for the disease.
The president is 74-years-old, putting him at higher risk of serious complications from the virus.
The White House physician said the president is expected to continue carrying out his duties "without disruption" while recovering.
Meanwhile, a White House official said on Friday morning that the president was experiencing mild symptoms but was working from the White House residence.
They said that: "The president is not incapacitated. He is actually working from the residence."
His staff was being kept separated from Trump's staff "out of an abundance of caution", the added.
The New York Times reported that Mr Trump appeared "lethargic" at a fundraiser in New Jersey last night.
The newspaper was also told by sources that his symptoms were "cold-like" and that he fell asleep on Air Force One on the way back from his rally in Minnesota on Wednesday night.
The president's physician said in a memo that Mr Trump and the first lady, who is 50, "are both well at this time" and "plan to remain at home within the White House during their convalescence."
Vice President Mike Pence, who lead the messages of support to Mr Trump, tested negative for the virus on Friday morning and "remains in good health," his spokesman said.
Many White House and senior administration officials were undergoing tests on Friday.
However, the full scale of the outbreak around the president may not be known for some time as it can take days for an infection to be detectable by a test.
Officials with the White House Medical Unit were still in the process of tracing the president's contacts, the White House official said.
Mr Trump was last seen by reporters returning to the White House on Thursday evening and did not appear visibly ill.
The diagnosis comes as the president has been trying to convince the American public that the worst of the pandemic is behind them.