The 30-year-old hammer victim was on a Queens-bound J train pulling into the Bowery station when his 53-year-old pal asked a stranger taking up two seats to make room.
The seat hog complied but that didn’t stop the 30-year-old man from getting into an argument with him and six friends he was riding the train with, sparking a fight.
One of the six friends repeatedly kicked the 30-year-old man in the head and chest, officials said.
When the victim tried to defend himself, his attacker’s friends jumped in — and one of them pulled a hammer out of his backpack and bashed the victim repeatedly with it.
The victim’s friend tried to shield the victim but was also beaten, witnesses told police.
The suspects fled the train at the Bowery station and have not been caught, police said.
First responders took both victims to Beth Israel Hospital with non-life-threatening wounds.
Friday’s attack comes as the NYPD is fighting a 20% increase in attacks in the city subway system.