Smith was impeached and tossed out of the state House months before Tuesday's election after being arrested in a federal sting for allegedly accepting a $7,000 bribe.
He was disowned by his political mentors, including Illinois Secretary of State Jesse White, who helped him before the March primary. He had been appointed to a vacant House seat in 2011.
Smith, who pleaded not guilty, was arrested on federal bribery charges a week before he won the primary.
He refused to resign or leave the ballot and Tuesday night declared victory over independent Lance Tyson as he led 63 percent to 37 percent, the Chicago Tribune reported
Smith said he would work to clear his name in court.
"I know it won't be difficult because I have people behind me," he said at an election party at the JLM Abundant Life Community Center in a predominately African-American neighborhood on Chicago's West Side.
Smith's campaign literature featured a photograph of him with then-state Sen. Barack Obama.
"I've been a Democrat all my life," he said. "I just want to enjoy this moment."
Smith can serve in office because the Illinois Constitution prevents him from being removed from office a second time for the same charges, but he would have to leave office again if he is convicted in federal court.
In another Chicago-area race, ailing U.S. Rep. Jesse Jackson Jr. easily won re-election over two opponents to secure a ninth term despite not campaigning as he is being investigated over alleged misuse of campaign funds and is under review by the House Ethics Committee for seeking an appointment to Obama's former U.S. Senate seat in 2008, the Tribune said.
Jackson, son of civil rights activist Jesse Jackson, had 64 percent of the vote in the 2nd Congressional District with two-thirds of the vote counted.
Jackson, 47, is at the Mayo Clinic in Rochester, Minn., where he was being treated for a second time for bipolar disorder. He has been on medical leave from the House of Representatives for five months and did not have a single campaign event or run a single television ad in the staunch Democratic district.
His only communication with constituents during the campaign was by a robocall and he voted by absentee ballot.
"Once the doctors approve my return to work, I will continue to be the progressive fighter you have known for years," Jackson said in a statement thanking voters. "My family and I are grateful for your many heartfelt prayers and kind thoughts. I continue to feel better everyday and look forward to serving you."