The debt-laden company announced on Wednesday that Orr would leave his job as the chief financial officer at the end of August. He will be succeeded by Chris Coughlin, the chief operating officer.
The news of his departure prompted an 11-cent rise in IPG's share price to $13.32 and comes less than a month after it emerged that the group was being forced to defend a class action accusing it of defrauding investors.
Orr was named as a defendant in the action along with his predecessor, Eugene Beard, and the former chief executives John Dooner and Phil Geier.
The lawsuit alleges Interpublic issued misleading financial statements linked to questionable accounting practices at McCann.