The incident happened around 2:15 p.m. at the bottom of the stairs leading to the station, but before the turnstile.
The 30-year-old victim was taken to Lincoln Hospital in serious but stable condition and is expected to survive.
The suspect fled the scene, and no arrests have been made. The motive is unclear at this point.
The station is near Yankee Stadium in the Highbridge section and serves the B, D and 4 lines.
Police had earlier blocked off some areas of the station, but the stabbing did not impacting subway service.