Service Employees International Union Local 1 officials made the announcement this morning outside the airport, which is one of the nation's busiest.
The workers say they want the public's support and wouldn't want to mess up anyone's holiday plans.
The union is helping the workers, who are seeking union rights and a $15 per hour wage.
They work mainly for private contractors at the airport and include baggage handlers, cabin cleaners, janitors, and wheelchair attendants.
It isn't clear how such a strike would affect operations at O'Hare.
The Chicago Department of Aviation has said it doesn't anticipate any disruption in service.
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