Y&R London, which rebranded from Rainey Kelly Campbell Roalfe/Y&R last week, has handled its advertising in the UK since 2010.
The review is being run by The Observatory International and does not affect the global business, which is led by Publicis London.
Ferrero Rocher is perhaps still best-remembered for its 1993 spot "The ambassador’s party". Its advertising was then created in-house. Banks Hoggins O’Shea/FCB took over the business in 1999.
In 2006, the brand tried to distance itself from the "ambassador" ads with a James Bond-style spot called "Dazzle", by WCRS. Y&R’s first work for Ferrero Rocher revisited the "dinner party" theme to promote the Ferrero Collection.
Y&R did not comment.
Ferrero, Ferrero Rocher’s owner, did not return a request for comment.