It happened aboard a southbound number 4 train at the Wall Street station at 12:31 p.m. on Tuesday.
The victim suffered a stab wound to his lower left torso and was rushed to Bellevue Hospital with non-life-threatening injuries.
Police say the victim is a 27-year-old man and they are searching for an older teenager who fled when the train arrived in the station.
The victim is not being cooperative with detectives.
So far, no arrests have been made.
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