Prosecutors filed charges -- including conspiracy, false statement, mail fraud, and wire fraud -- against Jackson on Friday, stating that the former lawmaker had used $750,000 in campaign funds for his personal benefit.
"I'm guilty, your honor," Jackson told U.S. District Judge Robert L. Wilkins on Wednesday.
Jackson resigned from Congress in November, citing both the investigation into his spending and ongoing health issues. Jackson spent much of 2012 on medical leave, receiving treatment for bipolar disorder. According to the Sun-Times, Jackson broke down several times during his court appearance, and was handed tissues by his lawyers.
"Tell everybody I'm sorry I let them down," Jackson later said outside the courtroom.
In a statement to the media after the hearing, Jackson's attorney said that his client had "turned a corner" in dealing with his health issues.
"It turns out that Jesse has serious health issues," Reid Weingarten said. "[W]e're going to talk about them extensively with the court. Those health issues are directly related to his present predicament."
Jackson's wife, former Chicago Ald. Sandi Jackson, was in the courtroom when Jackson entered his plea. She is expected to plead guilty to a charge of filing false tax returns Wednesday afternoon.
Jackson will be sentenced June 28. According to reports, he faces up to five years in prison.