Emergency crews were dispatched to the area near the QEW and Mississauga Road shortly after 8:30 a.m. ET.
Peel EMS said the man in his 30s fell almost 10 metres out of the tree.
He was transported in serious condition to St. Michael's hospital by Ornge air ambulance but police confirmed shortly after 3 p.m. this afternoon that the man had succumbed to his injuries.
The Ministry of Labour has be called into investigate.