The accident happened around 11:45 a.m. Monday at 12 Mary Ella Drive in Wilmington.
Rescuers say the man was working on the roof of a building that was damaged by fire back in March when he fell through and landed on the second floor.
When medics arrived they were unable to go up the stairs for safety reasons, so they had to bring the victim out through a window.
He was taken to the hospital by helicopter. The man is believed to be suffering from multiple fractures.
His name and exact condition have not been released.