Police, firefighters and EMS crews raced to the lab, located at 700 Bay Street near several major hospitals including Toronto General and SickKids, around 10:40 p.m., where they found the male researcher on the 11th floor.
Toronto police Duty Insp. Paul MacIntyre said the man was working alone, but managed to call 911 himself.
"He was asking for medical help, he stated he had been poisoned," MacIntyre said.
"Originally, he gave the wrong address," he said, adding emergency crews quickly zeroed in on where the research lab may be.
Firefighters wearing ventilators pulled the man, who appeared to be unconscious, from the building and immediately performed first aid.
The researcher was taken to hospital in serious condition.
Police still aren't sure exactly what chemical the man was exposed to or how he came in contact with it.
MacIntyre said the Ministry of Labour has been contacted about the incident.