Hoffman tweeted that the Marine, who he did not name, recently traveled overseas on official business and tested positive for COVID-19 on Saturday. He is currently being treated at Fort Belvoir Community Hospital.
The announcement so far marks the first positive case for an American servicemember stationed in the US.
Defense Secretary Mark Esper and the White House have been briefed on the development, Hoffman said.
This story has been updated to reflect additional background information.