The Chicago Sun-Times reports that Quinn backed out of Sunday's event after the newspaper raised questions.
Rezko was a fundraiser for ousted Gov. Rod Blagojevich.
Quinn campaign spokeswoman Elizabeth Austin says the governor agreed to have "an old friend" host a party for him. But he canceled when it was mentioned that it might have the appearance of impropriety.
Anthony Abboud worked under Quinn when he was state treasurer. He's also mentioned in Rezko's federal indictment.
Blagojevich appointed him to the state Teachers' Retirement System board. Rezko then told him to take direction from convicted fundraiser Stuart Levine.