The account moves from Iris, the incumbent, which will continue to work on global ad campaigns for Mini, as well as PR.
The review was initially run by AAR and then Roth Observatory, with BMW’s procurement team involved from the chemistry stage.
A spokeswoman for BMW confirmed The Brooklyn Brothers had won the integrated brief, which includes advertising, CRM and social, content digital work.
Jackie Stevenson, the founder and global managing director of The Brooklyn Brothers, said: "We are so delighted to have won the opportunity to work with such an iconic brand and a seriously modern and dynamic team, it’s exactly the kind of partnership we dream about at The Brooklyn Brothers."
Iris had held the UK account since 2012. Before that, the account was split between WCRS for advertising and Lida for CRM.
Dan Saxby, the chief executive of Iris, said: "We're proud of the impact we've had on the Mini business.
"In addition to winning awards across various disciplines, together we have achieved three record-breaking sales years and were on track to do that again this year. We wish them all the best."