According to the NYPD and FDNY, Dillon Waldren-Dickson was discovered severely injured inside the seven-story building on Snyder Avenue near East 25th Street in East Flatbush after the fire broke out on the fifth level at 10:30 a.m.
He was pronounced dead at the Kings County Hospital Center after being taken there.
A woman in her 50s and a guy in his 21s who were both injured in the fire were sent to the same hospital, where their conditions were described as stable.
Relationships between the victims were unknown at first.
According to the FDNY, one firefighter sustained serious injuries and two others sustained minor injuries.
106 firemen from 25 FDNY units responded to the incident.
The fire was brought under control about 11:40 a.m., according to the FDNY.