CFD said the fire broke out in the second floor of an apartment building in the West Town area's 800-block of North May Street.
CFD upgraded its response, and at one point, there was a mayday call for a trapped firefighter. But a few minutes later, that mayday call was cleared.
Flames could be seen shooting from the roof as crews worked in frigid conditions. They were able to extinguish the fire around 9:50 p.m.
All three of those injured were transported to hospitals, CFD said. Officials did not say how serious their injuries are or what conditions they are in.
How the fire started was not immediately known. Officials did not immediately provide further information.