Giuliani had dodged the virus for weeks as multiple people in his orbit tested positive.
Giuliani appeared at events such as Trump's election night party at the White House and a news conference alongside Trump's legal team, and most recently he attended election-related meetings with state lawmakers in Pennsylvania, Arizona, Michigan and Georgia. Each event featured attendees without masks, including Giuliani.
Some at the events, including Giuliani's son, tested positive for the virus afterward. In addition, Christianné Allen, his spokesperson, tested positive late last month and had been quarantining after the mid-November news conference, Salon reported.
Giuliani is the 20th person close to Trump who has tested positive for the virus since the election night party, according to an NBC News count.