Xerox is buying Affiliated Computer Services in a cash and shares deal worth $US6.4 billion.
Xerox is already the world's biggest supplier of digital printer and document management services.
The BBC reports the deal which takes the giant photocopier company into the fields of data management and technology outsourcing.
Shares in Xerox fell by 14% on Monday as investors reacted to the deal. ACS shares gained 16.5%.
Xerox said it would take on ACS's debt, worth about $US2 billion, as part of the takeover.
ACS provides information technology services to industries including telecommunications, retail, financial services and education. It will operate as a stand-alone firm.
