The positive tests comes just hours after the White House announced that senior aide Hope Hicks had come down with the virus after traveling with the president several times this week.
She is said to have first felt poorly on Wednesday evening, returning from a rally in Minnesota on the president's plane.
Hicks was quarantined away from others on the plane and her diagnosis was confirmed Thursday, according to an administration official, who spoke to the Associated Press on condition of anonymity.
But despite her symptoms as early as Wednesday evening Trump then continued with his schedule Thursday and traveled to and from his Bedminster, New Jersey golf resort to take part in two campaign events.
He flew then back to the White House later Thursday evening, when it was publicly confirmed Hicks had the virus.
His social media director Dan Scavino and press secretary Kayleigh McEnany, who were originally set to join him on the Thursday trip, were replaced at the last minute by other aides.
It is not known why the president's test took so long to come back or whether he was tested Wednesday evening when Hicks first began displaying symptoms.
Trump only said he and Melania were were in quarantine on Thursday evening, writing: 'Hope Hicks, who has been working so hard without even taking a small break, has just tested positive for Covid 19. Terrible! The First Lady and I are waiting for our test results. In the meantime, we will begin our quarantine process!'
THURSDAY: Donald Trump gives a thumbs up as he walks from Marine One after arriving on the South Lawn of the White House in Washington, DC, October 1, 2020, following campaign events in New Jersey hours before revealing he has COVID-19
The fundraiser in New Jersey on Thursday was behind closed doors but some in attendance posted to social media
Saturday, September 26: President travels to a rally in Pennsylvania with Hope Hicks
Tuesday, September 29: Hicks is aboard Air Force One with the president and Melania to travel to night's first presidential debate in Cleveland. She is seen leaving the jet without a mask
Wednesday, September 30: Hicks travels on Marine One and on Air Force One to a rally in Minnesota Wednesday.
She is understood to have felt poorly on the way back, quarantining on the presidential plane to get home.
Thursday, October 1: Trump still travels to New Jersey for a fundraiser
Hicks tests positive
Trump says he is awaiting test results before confirming he and wife Melania have tested postivie for COVID-19
Friday, October 2: A political rally in Sanford, Florida is cancelled
While the Centers for Disease Control and Prevention recommends that people who have been in close contact with someone with COVID-19 quarantine for 14 days, White House staffers are considered essential workers.
CDC's guidelines for exposed essential