In October Kevin O’Byrne replaced Martyn Phillips, B&Q’s long-time chief executive.
The former brand director and acting marketing director David Hutchinson also departed at the same time and the former 118 118 and Orange-marketer Chris Moss joined as the brand’s customer and marketing director.
The Karma Communications-owned agency picked up the £40 million business in November 2012 after a final shoot out against WCRS. BETC London and Dare had been involved in the pitch at an earlier stage.
Karmarama has created work for the Kingfisher-owned retailer including the Rob Brydon-voiced "unloved rooms" spot this summer encouraging people to do up their spare rooms.
A spokeswoman for Karmarama said: "Following in B&Q’s senior management, Karmarama can confirm that it has parted company with the retailer by mutual consent."
A B&Q Spokeswoman said: "We can confirm that we will not be working with Karmarama after the early part of 2014 and are currently looking at ways of strengthening the Customer and Marketing agency resource for next year."