No injuries were reported in the fire around 3 a.m. Tuesday at Irving Park and Hoyne.
The cause is still under investigation.
Fire crews let out six lines on the fire in the rear of a 30 by 75-foot building with commercial space on the first floor and residential units on the second and third floors, according to Fire Media Affairs.
Dispatch reports indicated back porches on the residential floors caught fire and the flames spread to the first-floor commercial space.
The fire was extinguished about 4:30 a.m., according to Fire Media Affairs.
The Sun-Times Media Wire contributed to this report.