Kitcatt Nohr triumphed in a contest against Archibald Ingall Stretton and Partners Andrews Aldridge in a process conducted by The Haystack Group.
The pitch was called by Christian Cull, the Waitrose marketing director, and follows a number of changes to the retailer's agency arrangements.
Miles Calcraft Briginshaw Duffy won the advertising account in November, when it merged with How, the agency launched by Ken Hoggins and Chris O'Shea in 2004. In June, Manning Gottlieb OMD won the media business.
Cull said: "Although all three of the final agencies were outstanding, we are looking forward greatly to working with Kitcatt Nohr and have been particularly impressed with their copywriting skills and use of the written word.
"Our main objective will now be for us to move forward this aspect of our marketing and for Kitcatt Nohr to work closely alongside our other agencies. We look forward to having their team's specialist skills on board."
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