The state senator from Bloomington got the business group's endorsement on Wednesday. The 3,500-member group has never endorsed a Democrat for governor.
Brady is up against Democratic Gov. Pat Quinn and the Green Party's Rich Whitney for the job.
Chamber president Doug Whitley says the chamber's board had lost confidence in the current administration.
Illinois is struggling with a $13 billion budget deficit and high unemployment.
Quinn has pushed for an income tax increase to help address the state's budget problems, something Brady opposes.
A Quinn campaign spokeswoman says Whitley has previously praised Quinn.