The move will see Fahey provide independent strategic advice to Unisys senior management in areas such as business development.
"I am pleased to be able to assist Unisys in assessing changing trends in political, legal and governance practices, and to support the continued growth of the organisation," he said.
A former federal Finance Minister, Fahey has held prominent roles in both the public and private sectors.
In addition to Unisys, he currently acts as a senior adviser to JP Morgan Chase Bank, and is a director of several companies and charities.
Joining Fahey as the other new appointment to the board is Gordon Wheaton. A former executive vice president for Visa International, Wheaton also held senior roles at the National Australia Bank.
The new appointments will join current board members Andrew Barkla, Unisys Asia Pacific vice president and general manager, and Mike Ettling, Australia-New Zealand managing director.