A total of four people have died in the District after becoming infected with COVID-19.
As of March 26, D.C. had a total of 267 confirmed cases of the novel coronavirus.
The mayor identified the man as Deputy Director of the Mayor's Office of Legal Counsel George Valentine.
Bowser said she learned on Thursday that he had tested positive for COVID-19, and was told on Friday morning that he had passed away.
"It's devastating for everybody, of course, and we just are very sorry," Bowser said.
The mayor added that they are currently informing other staff members.
All "non-essential" businesses in D.C. are currently closed, and the schools are closed through April 24.