Marshall joins the IoD on 15 July in the newly created director of public affairs role.
Reporting to director-general George Cox, Marshall's principal task is to oversee a revamp of the Institute's image.
Cox told PRWeek earlier this year he was keen to end a 'misconception' that the body was a 'stuffy club of pin-striped suits'. He added that he wanted to see more IoD involvement in government policy making (PRWeek, 3 May)
The PA director role was created following the decision by director of communications Steve Reardon to retire.
Marshall, who will head a three-strong team, worked at retailer Kingfisher and as a press officer to politicians including Margaret Thatcher and John Major.