The account was previously split between HTW and Mr Smith (formerly Interfocus).
However, following an internal review of the photocopier manufacturer's below-the-line agency arrangements, Xerox has appointed HTW as its sole DM agency.
HTW has been on Xerox's roster for six years, during which time it has produced award-winning work, including a business-to-business campaign that picked up a gold at the Campaign Direct Awards in 2005.
Interfocus secured a place on Xerox's roster in 2001, when it bought the business-to-business agency Grange Advertising.
Alex Craddock, the head of brand and marketing communications at Xerox, said: "This decision follows months of reviewing Xerox's DM requirements across Europe, not just for today but the years ahead too. HTW demonstrated time and again that, creatively, it is at the top of its game."
He added: "What will make the difference for Xerox is the planning input that is so essential in a competitive category. Getting HTW to lead our below-the-line activities made good business sense."