The account, which will be entirely with JWT from January 1, is currently split between it and DDB London. JWT has added 18 countries, including the UK, France and Russia, to the eight it already handles.
A JWT spokeswoman estimated that the UK business would be worth between £4m and £7m, and the agency also handles the brand in Asia-Pacific and Latin America.
A spokeswoman for the company said: "Knorr is Unilever Bestfoods' largest single global brand and we now handle 80% of the Knorr business around the world."
DDB will continue to handle Knorr across North America, the Middle East, Africa and Australasia.
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