The landing between the second and third floors in a building on 315 East 166th Street collapsed at 6 p.m.
Residents who live above the first floor were taken out of the building using a bucket truck, while FDNY worked to secure the landing.
One man was in the stairwell at the time, and was taken to Lincoln Hospital. His injuries are not life-threatening.
Residents of the building will not be allowed back inside until inspectors say it is safe - the management company expects that will happen on Sunday.
In the meantime, the Red Cross is helping people find temporary housing.
