Degorski showed no emotion as the verdict was read.
Attorneys were summoned back to court after only two hours of jury deliberation.
The jury foreman delivered the verdict forms and their decision was read in open court.
The jury found Degorski guilty of seven counts of first-degree murder, one count for each of the victims killed: Thomas Mennes; Marcus Nellsen; Guadalupe Maldonado; Rico Solis; Michael Castro; and the owners of Browns Chicken and Pasta, Richard and Lynn Ehlenfeldt.
Victim's relatives did not comment per the judge's gag order. But the Cook County state's attorney who was present for closing arguments made a brief comment.
"All I can say is I'm pleased with the verdict," said Anita Alvarez, Cook County state's attorney.
In 1993, the seven were closed the Palatine restaurant when Degorski and his high school friend Juan Luna arrived to buy the last meal of the day.
DNA and a palm print connected Luna to the crime scene. Luna was convicted in 2007 and is serving a life sentence.
There was no physical evidence connecting Degorski to the scene, but jurors heard from five witnesses who testified that Degorski admitted his involvement.
Among those witnesses was Degorski's former girlfriend Anne Lockett.
The case languished for years without resolution until she came forward in 2002.
Prosecutors argued that Lockett's testimony was backed up by other evidence, while the defense argued that there was no direct link to Degorski and that there was evidence of another suspect.
Degorski's family left court without commenting.
Degorski's attorney would only make only a brief statement.
"My focus now turns to the sentencing hearing and trying to convince this jury that the appropriate sentence is life in prison," said Mark Levitt, defense attorney.
As this is a death penalty case, the first phase in which the jury determines guilt or innocence concludes. The second phase determines if James Degorski is eligible for the death penalty the third and final phase determines if death is an appropriate sentence for the crimes. The second phase begins on Wednesday.