Terms of the deal were not disclosed, but it was sealed after a number of holding companies had considered investing in the agency.
General Atlantic will now own the stake that was bought by another private equity company, Francisco Partners, in a $71 million deal in 2001. AKQA said the deal with Francisco was always done with a five-year timeframe in mind, and that it appointed Morgan Stanley last year to look for new investors.
AKQA vowed that the deal with General Atlantic would allow it to pursue its independence, and General Atlantic has been keen to highlight its credentials in the media sector, pointing to investments in Priceline.com, E-trade and Saga.
Ajaz Ahmed, the chairman of AKQA, said the decision to go with a private equity company would not hamper its glo-bal expansion: "The holding companies made it clear they need us more than we need them. They largely exaggerate how much they can provide in terms of global resources - it's still a case of having to fend for yourself when an agency is part of their machine."
As for the decision to remain independent, Ahmed said that AKQA was outperforming on a global basis rival digital agencies that are part of a holding company.
The agency has been on a new-business winning spree, most recently picking up work from Microsoft, Diageo, Coca-Cola and McDonald's.
Anton Levy, the managing director of General Atlantic, said: "We will make our global resources available to AKQA, and we look forward to a long and productive association."