A 50-year-old man was slashed by three men who jumped him on the G train in Brooklyn, authorities said.

The victim had just boarded the subway at the Broadway station when the men approached and grabbed him from behind around 1 a.m. Wednesday.

The suspects knocked him to the ground and began punching and kicking him before one pulled out a knife and sliced him across the abdomen and left shoulder, according to police.

The victim was forced to give up $120 in cash before the men fled the train.

He was taken to Woodhull Hospital for treatment, cops said.