The incident happened in Ottawa at a Christian co-op building for seniors at 220 Viewmount Dr., near Merivale and West Hunt Club roads, at about 8:15 a.m. ET.
The man's legs were pinned and "severely crushed" between an elevator floor and the floor of the building, paramedics said.
He had been trying to get from the second floor to the first floor. It's not yet known how the man came to be trapped in such a way.
He suffered multiple fractures and other injuries, and was conscious when paramedics arrived. Paramedics managed to stabilize the pinned man until an elevator technician manually lowered the elevator to free him.
An administrator at the Eastern Ontario Christian Senior Co-op was not immediately available for comment.
In surgery on Tuesday, both of the man's legs were amputated, police said. He remains in critical condition.
The Technical Safety and Standards Authority is investigating, with assistance from police.