The deal means the agency's four founders, Paul Kitcatt, Marc Nohr, Vonnie Alexander and Jeremy Shaw, will now own more than 90 per cent of the agency.
The agency launched in 2002 with backing from Mentor, comprised of members such as the former ISBA director-general and Clarke Hooper founder John Hooper; the former Direct Marketing Association president Colin Lloyd, and the Clarke Hooper co-founder Clive Mishon.
Mishon, who remains as a non-executive director, will retain a minority holding in the agency. The agency has also created another non-executive director post, which it has yet to fill.
Nohr said: "We want to be in control of our own destiny."
Separately, the agency has promoted Lazar Dzamic to the new role of planning director. Dzamic adds the role to his existing responsibilities as the planning director of Kitcatt Nohr's sister digital agency Underwired. The role was previously handled by Nohr.
Dzamic joined Underwired in 2004 from EHS Brann, where he spent four years as a digital strategist. During that time he worked on accounts including Mini, Tesco.com, TheAA.com and Comet.