The man, whose name and age were not immediately released, appeared a little dizzy on the stairs about 7:47 a.m. and then tumbled off, FDNY officials said.
It wasn't clear where in the station he fell.
"The rescue companies — the companies on the scene — packaged him, lifted him out of the staircase and got him out to the street area," said FDNY Batallion Chief Chris Reginella.
The worker suffered head trauma and was treated at Bellevue Hospital, officials said.
The MTA did not provide further information.