A 24-year-old man, attempting to break up a fight, was slashed in the neck on a J train in Brooklyn Wednesday night, police said.

The man was on the train around 10:20 p.m. at the Marcy Avenue station when he tried to stop a fight between two other men, police said. One of the other men then slashed him in the neck with a knife, they said.

The victim’s injury was nonlife threatening, they said.

Police are looking for the two men who they said are believed to be in their 20s and were dressed in construction attire.