The victim, 19, was stabbed in the arm and shoulder just before 5 p.m. on East 124th Street between Fifth and Sixth avenues, police and fire officials said.
He was "bleeding a lot," a fire official said, but his injuries were not believed to be life threatening. He was taken to Harlem Hospital.
Cops took a man into custody shortly after the attack, a police source said. He had not yet been charged as of early Monday evening.
The nature of the dispute was not immediately clear, police said.