FD beat four other rivals to secure the account, which will see the agency address some of the PR fallout from Interbrew's legal action last summer against The Guardian, The Financial Times, The Independent, The Times and Reuters over a leaked document that detailed a possible bid for rival South African Breweries.
Interbrew won the right to force the papers to surrender the document, but later dropped its legal action.
Interbrew, which brews lager brand Stella Artois, remained tight-lipped over FD's role in forging fresh links with the media following the court case, but confirmed the agency would be handling media relations, IR, analyst relations and strategic counsel.
FD reports to Interbrew vice-president of corporate comms Corneel Maes, based in Belgium.
Maes said FD's campaign work will target 'a range of elements and audiences'.
He added that FD is the group's first retained City agency, although Tulchan was hired on a project basis last year.
It is understood that Tulchan and Brunswick were included in the five-way pitch process.
FD's brief mainly covers the UK, but Maes said that some work may involve overseas elements.
The agency will work with Interbrew's Belgian consultancy Creative Strategies, which is employed on a project-by-project basis.