According to Chicago police, the incident happened just after 11:30 a.m., in the 300 block of N. Dearborn in the River North neighborhood.
Police said two men, 27 and 36, got into a verbal altercation. The 27-year-old victim was stabbed first, police said.
The 27-year-old then stabbed the man back, striking him in the head and thigh, police said.
The 27-year-old was transported to Northwestern Hospital in an unknown condition.
The 36-year-old was transported to Northwestern Hospital in a stable condition. He is in custody and charges are pending, police said.
Area Three Detectives are investigating.