The two men boarded the train at Newark Penn Station when an argument broke out with another passenger, NJ Transit spokesman Paul Milo said.
All three men got off the train at the Elizabeth station on Broad Street, where things escalated and turned physical around 6:45 p.m., Milo said.
That's when the suspect pulled out a knife and stabbed both men, authorities said.
One man walked into the Elizabeth police station and collapsed, Martins said. He was taken to University Hospital, where he was in stable condition Monday Milo said.
The second victim was treated and released, Milo said.
No arrests had been made as of Monday afternoon.
The incident remains under investigation by the New Jersey Transit Police Department.
Click here to follow Daily Voice Saddle Brook-Elmwood Park and receive free news updates.