An off-duty auxiliary cop was stabbed early Saturday outside the Harlem bar where he works as a bouncer, police said.

The auxiliary officer, 24, was knifed in the back just after 2 a.m. when he tried to break up a fight between two unruly customers at the D’Milton Restaurant & Sports Bar on St. Nicholas Place near West 155th Street.

The officer was taken to Harlem Hospital. He was expected to recover from his injuires.

An armed suspect was seen fleeing the scene after the stabbing, cops said. No arrests have been made.