Crews responded a report of a fire just after midnight in the first floor of a six-unit apartment complex in the 500 block of North Central Avenue, according to police.
A 3-year-old girl suffered burns and was taken to Stroger Hospital where she was listed in critical condition, officials said.
A 57-year-old woman was also burned and was taken to Loyola University Medical Center where she was listed in serious condition, according to police.
Another woman, 83, was taken to Loyola to be treated for smoke inhalation. Police said she was in serious condition.
A 53-year-old man suffered smoke inhalation and was transported to West Suburban Hospital where he was in fair condition, police said.
The cause of the fire was not immediately clear but damage spread to multiple units in the building.
The Chicago Fire Department is investigating.