Bertolli will now begin a search for a new ad agency to handle the European account, which covers the UK, Germany, Belgium and the Netherlands.
The new agency will be required to create local adaptations of work produced by McCann Erickson New York, which has been working with the brand since 2003.
BBH's place on the Unilever roster is unaffected by the move. It handles creative duties for Lynx/Axe, Floral Becel, Omo, Surf and Vaseline.
It has handled the Bertolli account since 2001 and picked up a Gold Effie in 2006 for its work developing the business from a spread into an Italian food brand.
Unilever produces a range of products under the Bertolli brand, including its global market-leading olive oil, pasta sauces and savoury nibbles such as bread-based snacks Bruschettine and Focaccine.
It recently launched a range of frozen dinners in the US, with an ad spend of $11.8m (£5.9m) last year, according to Nielsen Monitor-Plus.