Kitcatt Nohr won the pitch against Archibald Ingall Stretton and Partners Andrews Aldridge in a process conducted by The Haystack Group.
The agency will be developing a customer relationship strategy for Waitrose, which involves retention activity to ward off competition from rivals and acquisition campaigns to support the supermarket's expansion plans.
Waitrose is looking to double its size nationally by extending its reach outside of the South-East, where most of its stores have been based.
The appointment of Kitcatt Nohr is the latest in a series of changes to the supermarket's agency arrangements. The advertising account moved into Miles Calcraft Briginshaw Duffy 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.
Vonnie Alexander, the Kitcatt Nohr client partner, said: "Not only is Waitrose a terrific brand, but it is also a terrific opportunity for direct marketing. We're looking forward to deploying direct marketing to strengthen even further its relationships with customers, and also to win new converts to the brand."
Christian Cull, the marketing director at Waitrose, said: "We are looking forward to working with Kitcatt Nohr.
"Our main objectives will be to move this aspect of our marketing forward and for Kitcatt Nohr to work alongside our other agencies."