The residents were inside the Ketcham Street home when heavy fire broke out just before 4:30 a.m.
The most seriously injured, a woman in her 30's, suffered burns to her face and abdomen. She was rushed to the Cornell burn unit at New York Presbyterian Hospital.
The other residents, including a 12-year-old girl, were treated for smoke inhalation at Elmhurst Hospital. The six people inside were fast asleep and woke up to intense smoke in every room of the house.
Three firefighters were treated for minor injuries. One went to Elmhurst Hospital, the other two were treated at the scene.
The FDNY stopped the flames from spreading to several other homes, limiting the structures to exterior damage.
The flames were so intense they jumped to neighboring buildings, forcing people to climb down to safety from the fire escape.
Marvin Mercado was fast asleep with his friend Eman Villamin. She woke up to the loud sounds of popping and crackling, screamed for her aunt and realized they were trapped.
"She opened the door and there was a big fire already and we couldn't get it out it was too close, and it's so hot we were trapped in there," said Villamin.
Firefighters received calls from multiple other buildings on the block of people in distress, but all residents got out safely.
The cause of the fire is under investigation.