The fire broke out around 11:30 a.m. in the 43-hundred block of 18th Avenue in Borough Park.
The building contains a store on the lower level and apartments on the second and third floors, where the fire started.
The fire reached two alarms before firefighters knocked down the flames.
Authorities reported 14 injured, including a dozen firefighters. Most of the injuries were minor, officials said. One firefighter was treated for smoke inhalation.
The victims were taken to Kings County Hospital, Lutheran Medical Center and Maimonides Hospital.
The Red Cross is helping some of the residents, officials said.
The cause is under investigation.