It’s understood the man fell from the roof of a building undergoing renovation on Irving Road in Toorak just after 7am.
After falling a distance, it’s understood he became impaled on a timber post.
Fire Rescue Victoria crews performed a high-angled rescue, cutting the timber down and transporting the man to a flat surface.
He was then taken by Ambulance to The Alfred hospital with critical injuries.
Work Safe is investigating the incident.