The FDNY said it responded within two minutes, but it took nearly four hours to get the fire at 244 Montrose Ave. near the corner of Bushwick Avenue under control.
The initial 911 calls came in around 6:10 p.m.
The FDNY tweeted out video of the fire to let people in the area know what was happening.
More than 200 firefighters and EMS responded to the scene to put out the fire.
Fire officials said the fire spread from the second floor up to the third floor and over to the buildings on each side.
They said crews began to tackle the flames from inside the building, but were forced to go outdoors and attack it from various angles as the fire spread throughout. Overall, four buildings were evacuated.
The fire chief said the buildings in the area are old and constructed from wood, which contributed to the flames spreading quickly.
The Department of Buildings said there were multiple collapses inside the building where it started and extensive damages to at least three other buildings.
The Red Cross said it helped six families, comprising of a total of 26 people, with temporary lodging, financial assistance, as well as items like blankets, water, hygiene items and clothes.