Police say the 30-year-old man was attacked while on the G train platform with his brother just before 10 p.m.
They reportedly got into an argument with two other subway riders, and punches were thrown.
One of the assailants then pulled a knife and stabbed the man in the leg and lower back, according to authorities.
The stabbing victim was hospitalized in stable condition.
Two men were being questioned, but no charges were immediately filed.