Around 20 people moved into Roman House near the Barbican in the City of London which is owned by Berkeley Homes.
The Occupy campaigners had said they planned to “open the building to the public” today.
But Naomi Colvin, of the group, said they had moved out to avoid putting builders jobs at risk.
She told the BBC: “Contractors employed by Berkeley Homes contacted us directly and asked us to reconsider.
“While they fully supported our cause they had expressed concerns about their project being mothballed due to our presence on the site.”
Berkeley Homes said the building was not safe for public use
A spokesman said: “There are holes in the floors and we are in the early stages of asbestos removal.”