It happened Saturday outside the Union Square subway station.
According to the NYPD, the 29-year-old victim had exited the station at about 11:40 a.m. when the suspect approached him from behind and used an unknown object to slash him on his back.
The victim chased the individual into the East 14 Street/Union Square subway station, where he boarded a northbound "6" to parts unknown.
The man was taken to Beth Israel Hospital for treatment to his injury.
Police released a photo of the man they are looking for:
The NYPD describes him as a male Hispanic, light complexion, approximately 35-40 years of age, last seen wearing a camouflage shirt and dark sunglasses.
Anyone with information is asked to call the NYPD's Crime Stoppers Hotline at 800-577-TIPS or for Spanish 1-888-57-PISTA (74782)