A United Nations diplomat from the Caribbean allegedly punched his wife in the face in Brooklyn on Friday — but NYPD cops couldn’t arrest him because he has diplomatic immunity, police sources said.

Sehon Marshall, 43, who serves as a counselor for the Permanent Mission of St. Vincent and the Grenadines, allegedly decked his wife, Sandra Marshall, 36, after a verbal fight broke out at their Canarsie house at 1:15 a.m., police sources said.

Cops launched an investigation and found that Marshall struck the woman with a closed fist, leaving her with a bloody lip, the sources said.

But officers couldn’t bust the thug-in-a-suit — because he’s protected by a law forbidding prosecution of foreign diplomats in the US, the sources said.

In August 2014, Marshall enraged supporters back home when he bashed immigrants who “quit their jobs and migrate to the United States to become nannies and dog walkers,” according to the Caribbean media site CANA News. He made the comment while defending the country’s Unity Labour Party on a radio show. He later apologized.

Marshall was once a host of the Unity Labour Party’s radio station, according to past reports.

His Facebook page notes he is a former deputy consul general at the Consulate General of St. Vincent and the Grenadines to the USA.

Marshall wasn’t available for comment at his home on East 92nd Street and Avenue N on Friday afternoon.

His wife, who refused medical attention, declined to comment.

Additional reporting by Shawn Cohen and Abigail Gepner