Giuliani has traveled extensively to battleground states in recent weeks in an effort to help Trump subvert his election loss.
Giuliani made an appearance earlier on Sunday on Fox News to speak about his legal challenges in several states on behalf of Trump.
The diagnosis comes after some very public missteps from Giuliani, who was at centre of the Four Seasons Total Landscaping debacle and was also recently accused of audibly breaking wind at a recent hearing into alleged election fraud.
At that same hearing he asked a woman testifying if she felt comfortable removing her mask.
Giuliani is the latest member of Trump's inner circle to test positive and his own son Andrew tested positive last month.
Additional reporting, Associated Press
- More to come