The FDNY responded to the fire on the top floor of a rowhouse on 55th Street in Sunset Park just before midnight.
Sixty firefighters responded to the scene and placed it under control about an hour later.
Two people, including the firefighter, were brought to NYU Brooklyn Medical Center with non-life threatening injuries.
Two more people were treated at the scene.
Investigators are trying to determine how the fire started.
ALSO READ | 'Curtain Up' festival in Times Square celebrates return of Broadway
'Curtain Up' festival in Times Square celebrates return of Broadway
----------
* More Brooklyn news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube