In a statement on Tuesday, his office said the 73-year-old Republican governor was "experiencing mild symptoms" and was isolating at home with his wife, Peggy, who tested positive for the virus on Friday but is asymptomatic.
McMaster was tested after "coming into close contact with the COVID-19 virus," the results for which came back late Monday, the statement said.
His wife had tested positive for the virus after attending a White House Christmases event last week.
McMaster is the latest governor to test positive for COVID-19.
Earlier this month, Pennsylvania Gov. Tom Wolf was also confirmed to have contracted the virus.
Colorado Gov. Jared Polis, Virginia Gov. Ralph Northam, Missouri Gov. Mike Parson, Oklahoma Gov. Kevin Stitt and Nevada Gov. Steve Sisolak are among the governors who have contracted the virus.
The announcement of McMasters' illness came as the United States continues to battle climbing coronavirus cases. At more than 18.2 million infections, the United States is by far the sickest country in the world to the pandemic, according to a live tracker of the virus by Johns Hopkins University.
South Carolina's Department of Health and Environmental Control reported 2,055 new cases on Tuesday for a total of more 277,000 confirmed and probable infections and nearly 5,000 deaths.