The account will be led by the agency’s London office. It will include eBay’s key markets - Germany, France, Italy, Spain and the UK.
Naked won the account following a pitch process that was run by eBay with the support of Creativebrief. The pitch kicked off in July.
The brief consolidates work previously held by Essence and Achtung! EBay’s advertising and media planning and buying briefs are unaffected.
Naked will now run the owned and earned aspects of social media for the company, including talking to its 2.5 million Facebook fans and creating "newsfeed worthy" content.
Bas Ellen, the European head of social media at eBay, said: "EBay provides the perfect sweet spot between utility – getting what you want, when you want it – and engagement – being inspired to shop the world.
"We needed a partner who can help unlock the strength of this unique positioning and engage with both the ‘heart’ and ‘head’ of our social media and content programme. Naked has shown this from day one."
EBay hired MediaCom to its £80 million pan-European media account in May 2014. At the time eBay said it would continue to work with the incumbents Carat, Fetch and Essence.