Police say the 74-year-old was trying to swipe his card at a turnstile.
The attacker, who was at an adjacent turnstile, then punched the man in the face and ran off.
It happened on Tuesday at 11:20 a.m. at the D line s Kingsbridge Road station.
The victim went to Montefiore Hospital for treatment of neck pain, but was expected to be ok.
Anyone with information in regard to this incident is asked to call the NYPD s Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).