The appointment follows a review of the UK business at the start of the year and will result in a new direction for the brand's advertising.
Having pitched against BMB and MCBD, the agency will now create through-the-line advertising and oversee brand strategy.
The campaign will be Yeo Valley's first work since activity highlighting a rebranding and repackaging, created by Publicis, rolled out at the start of 2008.
The activity introduced the strapline 'A breath of fresh air from the country'. Publicis however parted company with Yeo Valley late 2008, having picked up the account in October 2006 after a pitch against undisclosed agencies.
Launched in 1993, Yeo Valley is a family owned business that as well as yoghurt, also produces cheese, ice-creams, butter and milk.
The company is part of Organic UK, a trade body set up to help drive sales of organic products that also includes Green & Black's, Organix and Rachel's.
Ben Cull, head of brand marketing at Yeo Valley, said: "2010 sees the organic market entering a new stage in its development, and as such we too have to ensure that the Yeo Valley brand evolves so that it continues to be relevant to today's consumer.
"Our appointment of BBH will see a fresh direction, helping to take the brand to its next level."
Ben Fennell, chief executive officer of BBH London, said: "In many ways this was the dream pitch opportunity, a great business, brilliant products, nice people, loads of ambition. I am really excited about we can achieve together."