The first-term Democrat woke up with a raspy voice Sunday and took a PCR test that came back positive, spokesperson Fabien Levy said in a statement.
Earlier Sunday, Levy had tweeted that Adams had taken a rapid test that came back negative but took the additional test out of an abundance of caution.
She says the mayor has no other symptoms, but is "already isolating and will be canceling all public events for the remainder of the week."
"He is also going to immediately begin taking the anti-viral medications offered for free to New York City residents and encourages all New Yorkers eligible for these medications to take them as well," Levy said. "While he is isolating, he will continue to serve New Yorkers by working remotely."
Adams is now the latest in a long list of high-profile attendees at last week's Gridiron Club dinner in Washington D.C. who have tested positive for COVID. Organizers of the Gridiron dinner say that there were 72 positive cases reported.
"Now eight days after the dinner, the connection between a new positive test and our dinner is certainly arguable, particularly for public officials who have had a full week of public events," organizers said, in part.
The announcement is unfortunate timing for the mayor, who on Sunday, marked his 100th day in office.
"When I became mayor, I made a simple promise to New Yorkers to 'Get Stuff Done,' and we've done just that over the last 100 days," Mayor Adams said in a statement.
Adams was scheduled to attend an official ribbon cutting event on the Coney Island boardwalk to celebrate the opening of Deno's Wonder Wheel.
The mayor and New York Governor Kathy Hochul were both in Albany on Saturday attending a conference.
New York City has been experiencing a steady resurgence in virus cases over the past month.
It's now averaging around 1,800 new cases per day - not counting the many home tests that go unreported to health officials.
That's triple the number in early March, when the city began relaxing masking and vaccination rules.
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The Associated Press contributed to this report
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