The crime happened at about 3:15 a.m. in the 6500-block of W. Fullerton Avenue, police said.
A man, 27, was outside when police said he was robbed and then got into an altercation with the suspect.
During the altercation, police said the suspect shot the 27-year-old victim and ran away.
The victim was shot in the leg and abdomen; he was taken to an area hospital in "fair" condition, police said.
Nobody is in custody. Chicago police are investigating.