The decision was part of an "ongoing comprehensive review" of security measures at the White House and its surrounding grounds, the agency said.
It comes one month after a man armed with pepper spray jumped the fence and was inside the grounds for 16 minutes.
Two Secret Service agents who were on duty that night were fired.
President Donald Trump was there at the time, but the intruder did not make it into the White House building.
The new restriction moves public view on the south side of the White House about 82ft (25 metres) farther back from where people were previously able to stand.
Secret Service Communications Director Cathy Milhoan said on Wednesday "that vantage point... is still there. It's just a few feet further back".
A higher fence has also been approved for the White House, she told WTOP News.
The White House will begin viewing bids later this year, with construction to begin next year.
In 2014, a second barricade was erected on the northern side of the building in response to a fence-jumper who was able to run through the doorway of the building while carrying a knife.
That incident prompted Julia Pierson, the first woman to lead the agency, to resign.
The US Secret Service has announced it has permanently closed access to a sidewalk along the perimeter of the White House.