Police said the victim was minding his own business on the train when a man went after his gold chain.
Investigators said a struggle ensued, a gun was pulled out and the victim was shot one time in the side.
He was taken to the hospital. Authorities said he was expected to survive his injuries.
Police said the suspect ran from the subway. He was spotted running on 53rd Street toward 8th Avenue when officers chased him down.
He was also taken to the hospital with unknown injuries.