Staff discovered the intrepid visitor on the 72nd floor of the Shard building at London Bridge, 944ft above the ground.
The animal, nicknamed Romeo by staff, entered the building through a central stairwell before climbing to the top. It was living off scraps left by builders.
Pest controllers from Southwark Council eventually caught the fox after two weeks and took it to an animal sanctuary. It has since been released near London Bridge.
Les Leonard, a pest controller, said: “At first I didn’t believe it was up there, I thought it must be a hoax. I’ve got a fear of heights and getting the hoist lift from the 35th floor to the 72nd was terrifying.
“On the second day it ran straight past us then scrambled up a 10 foot ladder onto the rafters. It was surreal, we couldn’t believe that a fox could go that high.”