The 32-year-old victim was attacked around 10:30 a.m., at Sutter and Christopher avenues in Brownsville, according to the New York City Fire Department.
He was taken to Brookdale Hospital in cardiac arrest, where he was later pronounced dead, officials said.
The motive is unclear, but it appears the two may have been fighting over a woman.
The case is under investigation.
Police are looking for a man in his 50s who fled the scene.