It happened on the southbound No. 1 tracks at the 18th Street station in Manhattan's Chelsea neighborhood just after 1:30 p.m. local time.
The 45-year-old victim was taken to Bellevue in critical but stable condition.
SEE ALSO | NYPD identifies woman set on fire and killed on Brooklyn subway train
The suspect ran away but authorities said they had a man in custody who was being questioned shortly before 4 p.m.
Few other details were immediately released.