The move ends months of speculation about the future of the account, which moved to Saatchis in September 2006, following a pitch against McCann, DDB and Publicis.
During the pitch process, all of the agencies were asked to submit ideas for a Christmas campaign, but were told that the winner would not necessarily pick up the account. McCann won that brief, but not the overall business.
However, McCann's senior management team has since continued to forge strong links with Sony Ericsson, fuelling speculation it might pick up more work at some point.
The Sony Ericsson account was put up for pitch after the company split with Bartle Bogle Hegarty, its agency of five years in July 2006.
Dee Dutta, the corporate vice-president and head of marketing for Sony Ericsson, said: "I can confirm that Saatchi & Saatchi remains, and will remain, a partner of Sony Ericsson."