Officials said the man, about 200 pounds with brown eyes, started having sex with a woman in front of other subway riders on the platform for the Nos. 4 and 5 subway trains.
Officials said the incident was witnessed by "multiple customers" inside the station.
It was not disclosed if the couple then got on a train or left the station, but officials released a photograph of a man wanted for public lewdness. An image of the woman involved in the incident was not released.
Anyone with information in regard to the incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS, or submit tips by logging onto the CrimeStoppers website, or on Twitter @NYPDTips. Police said that all calls are strictly confidential.