Police say the victim was seated on an A Train going southbound at the Hoyt-Schermerhorn Street subway station.
They say a male suspect kicked the victim's foot and the two got into a verbal dispute.
The suspect then stabbed the victim in the stomach and arm.
Officials say the suspect then fled from the train.
The victim was taken to Methodist Hospital in serious but stable condition.
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"This afternoon's stabbing at Hoyt-Schermerhorn is an outrageous act that is completely unacceptable. We will continue to work with law enforcement to make sure the system is safe for our customers," New York City Transit Interim President Sarah Feinberg said.
No arrests have been made and the investigation is ongoing.
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