The Samsung Life building received a bomb threat at around 11:30 a.m. (local time), the Korea Times reported.
The building is one of three Samsung buildings at the site, with the other two occupied by Samsung Electronics and Samsung C&T.
The company evacuated about 3,000 staff from the Samsung Life building.
"We immediately evacuated the building after receiving the bomb threat," the Samsung official said. "This is an actual situation and not a drill."
Police are searching for any explosives, the report said.