The food delivery app is hoping the move will increase orders for local restaurants , which have been closed to in-person dining.
"We're removing barriers like high fees that often prevent diners from ordering delivery, during a time when dine-in service isn't allowed for restaurants in Chicago.," the company said in a release.
Diners have until December 31 to sign up for Grubhub+ for the three months of free delivery.
Each Chicago restaurant already signed up for Grubhub will automatically be upgraded to Grubhub+ until mid-March at no additional cost.
Registered Grubhub users will receive an email to opt-in for the special perk.