The contract, worth as much as $160 million annually, replaces an existing IT outsourcing contract that was to expire in April.
"Signing this new agreement with CSC demonstrates the success of our long-standing business partnership," said Dean McCumiskey, BAE Systems global chief information officer.
"As the defense industry continues to evolve, CSC's expertise and support in delivering highly competitive, value for money services across our business in support of our strategic and operational objectives will be invaluable."
CSC services covered by the new award include collaborative services, end-user compute, mainframe, physical/virtual servers, storage and networking.
Also part of the contract are service request fulfillment and project services and application maintenance and support.
CSC and BAE Systems first signed a 10-year IT outsourcing contract in Britain in 1994. Through the new agreement, CSC provides IT services in support of 11 BAE Systems businesses in more than 100 locations in Britain, Saudi Arabia and Sweden.