The Bio Agency will now be responsible for creating digital campaigns, with a particular focus on social media, to help Selfridges build better relationships with its consumers.
Its first campaign for the brand will focus on raising awareness of Selfridges' new shoe department, which launches in London later this month and will be the largest shoe hall in the world.
The work will also aim to highlight that all of the products will now be available to view online for the first time.
The Bio Agency was launched in 2006 by the former glue Isobar account director Paul Glossop, the freelance creative Robin Souter and the MBA account director Peter Veash.
Selfridges is also holding a pitch for its ad account. 18 Feet & Rising, Engine and VCCP have been shortlisted.