Earlier, Winfrey told reporters she didn't think she would be picked because she is too opinionated. But she said if she was picked, she hoped the trial wouldn't take too long.
"I'm just hoping it doesn't take longer than a week because I've got shows to do," she said.
The billionaire walked into the courthouse Monday morning through a special entrance to avoid the crowds. But officials said she wouldn't receive any other special treatment as she does her civic duty.
After Winfrey was selected, Judge James B. Linn was asked how she was picked.
"This was a straight up jury selection," he said.
Winfrey was scheduled to appear at court along with some 300 other prospective jurors, Cook County sheriff's office spokeswoman Sally Daly has said.