Cook County Circuit Court Associate Judge Susan Coleman signed off on the request Friday from prosecutors and the medical examiner.
Urooj Khan, 46, of West Rogers Park, died in July. At the time, investigators did not believe his death was suspicious.
At the urging of a family member, investigators revisited the cause of death. That's when a Chicago medical examiner determined that Khan had died of cyanide poisoning.
The death has since been ruled a homicide.
Medical Examiner Stephen Cina says he hopes to gather additional evidence through more tests on the body that could be presented in court.
"That's the only way to figure out what happened," Khan's brother-in-law Mohammed Zaman said.
Khan's sister also hopes the exhumation will help the investigation.
"It's very hard because I wanted my brother to rest in peace but then we have to have justice served. So if that's what it takes for him to bring justice and peace, then that's what needs to be done," said Meraj Khan, who was present at the hearing.
At the family's dry cleaning business on Thursday, Khan's widow Shabana Ansari declined to speak on camera. However, she told ABC7 that she supports the effort to exhume Khan's body from Rosehill Cemetery. She believes the exhumation will "reveal the truth."
Ansari said she and two other family members ate what turned out to be Khan's last meal in July.
Meanwhile, ABC7 has learned that Ansari's father has two federal tax liens against him- one for $93,000, and a second for more than $31,000, totaling nearly $125,000.
The elder Ansari, who was also present at the family's dry cleaning business Thursday, declined to comment about the liens.
Khan is survived by Ansari and a teenage daughter from an earlier marriage.
The lottery money, as well as Khan's other assets, are part of an on-going probate case between his widow and his brother.
Khan's brother, through court documents, says he wants to make sure Khan's teenage daughter from a previous marriage receives her share of assets.
Meraj Khan, who now has custody of the teenager, would not say whether or not the girl has been questioned by police.
"She is very devastated," Meraj Khan said. "It's very hard to have her home and see her upset and I'm trying to cheer her up."
Arooj Khan was generous and wanted to share the lottery winnings with those in need, according to his sister. "He was just excited about helping than even doing something for himself," she said. "So you can see what kind of person he is." The Associated Press contributed to this story.