The shooting occurred inside Mr. G's Entertainment Center in the Gresham neighborhood after a fight broke out around 1 a.m., the Chicago Tribune reported.
Three gunmen opened fire, striking seven people. It was not clear whether the gunmen were among those shot.
All of the wounded were transported to local hospitals, where they were all listed in stable condition.
Police said the incident appeared to be gang-related but the cause of the fighting and shooting was unclear, the Chicago Sun-Times reported.
No arrests have been reported.
A poster said rap artists Nino, King Samson and Lil Mouse were to perform at the event.
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Aaron Carter is still in love with Hilary Duff