The account, which was split between JWT and DDB London, has been consolidated into the one agency without a formal pitch.
JWT already held the brand in eight Northern European markets but the review sees it adding 18 new regions including the UK, Italy, Spain and France.
DDB will continue to handle the brand in North America, the Middle East and Africa, and Australasia.
UK advertising for Knorr has included a campaign for its Vie soup range that claimed the soup could provide three out of the five recommended daily portions of vegetables. A TV ad featured a naked girl with cucumber on her body and the endline: "How you get the rest of them is up to you."
Paul Hammersley, the chief executive and chairman of DDB London, said: "We have a successful, ongoing campaign in the UK and it is our understanding that this will continue next year."
Knorr is sold in more than 100 markets and has sales of around £2 billion.