M&B won the account after a competitive pitch and will work alongside Knorr's global agency partners J. Walter Thompson, DDB, Initiative and MindShare to supplement the advertising and media work of these agencies.
The UK will be a key market.
This is the second piece of business M&B has won from Unilever Bestfoods.
Last July, the agency won a £20 million pan-European brief for its Family Brands business.
Charlie Stopford, Unilever Bestfoods' media manager, said: "My brief is to bring brands to life as part of a consumer's everyday experience so as to maximise Unilever's media investment. We continue to award business to M&B because it understands how to achieve this."
Paul O'Neill, a partner at M&B, added: "Growing our Unilever relationship is a big priority for us. Knorr is Unilever's biggest brand."
Knorr is one of the world's biggest culinary brands, with annual sales of about £3.5 billion. Last year, Unilever indicated that it was planning to spend £15 million supporting it in order to establish it as a top ten power brand by 2005.
Last month, M&B further strengthened its FMCG credentials after winning a brief from GlaxoSmithKline for its Aquafresh brand. The agency was appointed to undertake a product development project for the brand.