Firefighters battled the bitter cold to put the fire out inside the building on the 3800-block of South Ellis.
A 30-year-old victim suffered smoke inhalation according to the Fire Department.
The man was taken to the University of Chicago Medical Center in critical condition, fire officials said.
The blaze was put out by about 3:40 a.m., according to fire officials.
The cause of the fire is now under investigation.
The Sun-Times Media Wire contributed to this report.