BMB will be charged with increasing footfall at Selfridges' London, Manchester and Birmingham department stores. An ad campaign, which will focus on new aspects of the store, will break later in the summer.
Selfridges called the review after Mother, the incumbent agency of three-and-a-half years, resigned the account. Mother decided to resign the business after the department store invited other agencies to pitch for its Christmas 2006 campaign.
The BMB founding partner Trevor Beattie, said: "There's no company like Selfridges; it's a client that is genuinely made for us and gives us a chance to fulfil the promise on which we set up."
BMB's founding client, French Connection, has a concession in Selfridges.
Mother won the Selfridges account in December 2002 after the department store consolidated its marketing into one agency.
The agency created a series of integrated press, poster and in-store campaigns including "body craze" and "Brazil".
Mother's most recent print campaign for the retailer featured women's products, including make-up and handbags, shot as if they were catwalk models.