Police said the men were discovered unresponsive in a Jeep Cherokee in the Calumet Park neighborhood's 12300-block of South Halsted just after 8:30 a.m.
Both men appeared to have multiple gunshot wounds throughout their bodies and were pronounced dead on the scene, police said.
What led up to the shooting was not immediately clear. Police did not immediately provide further information.
Area Two detectives are investigating.
INTERACTIVE SAFETY TRACKER Track crime and safety in your neighborhood