It happened near Wednesday morning just before 10:30 a.m. on the city's Upper West Side.
The victim was walking with another person when an unknown male jumped him from behind, slashing him in the side of the face, ear and neck, causing a deep laceration.
The suspect yelled 'f- you guys' after slashing the victim, according to police.
The victim was treated at a nearby hospital and is expected to recover.
The suspect is described as a man wearing a gray short-sleeved shirt and dark colored sweats.
Residents in the neighborhood said any kind of violence in their community is a problem, but when it appears to be random, it makes things even more alarming.
"I mean, it looks like just an average person on the way to the gym or something, he wouldn't even look twice at this person," said neighbor Liz Stroscio.
The slashing comes the same week as the fatal stabbings of three people in unprovoked attacks elsewhere in Manhattan. A man is charged with three counts of murder in that case.
Anyone with information on the slashing is asked to contact police.