The collapse happened in the 2300 block of Heritage Center Drive in Furlong, Pa. around 8:30 a.m.
It took firefighters an hour to pull the worker from the rubble in what was called a 'delicate' operation.
"We treated him for crushing injuries prior to his extrication," said Charles Pressler of the Central Bucks Ambulance and Rescue Unit.
The injured worker was flown to Temple University Hospital in Philadelphia.
The name of that worker has not been released.
The collapse is under investigation by OSHA and Buckingham Township officials.
There was no immediate word as to why the building collapsed.
By Thursday afternoon work had begun to stabilize the building.