Under the terms of the 10-year deal, IBM Global Services will manage the IT operations of Cendant's 40 business units, which include Avis Rental Cars and National Car Parks.
Cendant believes the deal will improve customer service and support future developments, but outsourcing consultant Robert Morgan questioned the "one size fits all" nature of the deal.
"All of Cendant's businesses have different values which are not suited to a blanket deal," he said. "How will Cendant get a cohesive picture of how IBM is performing across such different businesses?"
IBM will run Cendant's 1,400 servers and host many of the Web sites and interactive services operated by the corporation's brands. It will also assume responsibility for the IT operations of third parties that are currently outsourcing these functions to Cendant.
IBM will also provide helpdesk and desktop support services to Cendant's Avis, Wizcom and real estate businesses.