Citizen Relations held the account for several years before it was put out to a competitive pitch in November last year. The account is thought to be worth in the region of £1m per year.
Fever board director Paul Lucas said the agency would be harnessing "Sony's historic challenger mentality" to deliver campaigns that highlight Xperia's "innovation" story.
"From the release of the Walkman phone to the first camera phone with a flash and waterproofing smartphones, Sony has always challenged convention," Lucas said.
Fever will handle Sony Mobile's UK press office and will work alongside media buyer Mediacom, integrated agency Hey Human and creative firm Haygarth on the retail launch of the XZ Premium smartphone and the Internet of Things-enabled Xperia Touch projector, which were unveiled at Mobile World Congress in Barcelona earlier this year.
Matt Beavis, head of PR, social media & sponsorships at Sony Mobile, said: "Sony is once again at the forefront of innovation, bringing 4K HDR and super slow motion camera functionality to smartphones and creating projection technology that turns any surface into a touch screen with the release of the Xperia Touch."
Sony Mobile was founded in 2001 as a joint venture between Sony and telecoms equipment specialist Ericsson. In 2012, Sony acquired Ericsson's share in the business.
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