Six adults and one child were in the block in La Crosse Terrace, Kelvinbridge, when the staircase collapsed in the early hours of yesterday morning.
They were evacuated through a window.
Fire crews were called to investigate after a friend of a resident reported the collapse at 2.25am.
They advised the residents to stay in their homes while fire officers met with council officials.
They decided the stairs were too unsafe to use and residents needed to be evacuated.
Two women and one man were rescued from the third floor window by fire officers using a high reach aerial rescue pump.
A third woman was rescued by a ladder.
This morning, the building was cordoned and a sign above the door warned the building was unsafe.
A Glasgow City Council spokesman said: "On the evening of September 8, the close staircase began to fall away in this tenement.
"As a result the residents were evacuated and the building and staircase is now propped up and has been deemed a dangerous building."
A spokesman for Scottish Fire and Rescue said a staircase had collapsed between the first and second floor.