The company had previously confirmed it was in discussions with the private equity firm after reports emerged that it was looking to cap an auction for the business.
A WPP spokesperson said at that time there was no certainty the discussions would result in a transaction involving Kantar as Mark Read, chief executive of WPP, had previously stated his intent to hold onto 25-40% of the company.
However, a statement from WPP said the sale will allow it to strengthen Kantar with the expertise and resources of Bain Capital.
“Kantar is a great business and we look forward to working with Bain Capital to unlock its full potential. As a strategic partner and shareholder in Kantar, WPP will continue to benefit from its future growth while our clients continue to benefit from its services and capabilities,” said Read.
“I would like to thank Eric Salama, his team and everyone at Kantar for their tremendous contribution to WPP – a contribution that will continue as we develop the business together.
"This transaction creates value for WPP shareholders and further simplifies our company. With a much stronger balance sheet and a return of approximately 8% of our current market value to shareholders planned, we are making good progress with our transformation.”
You can read The Drum's interview with Read on the sale here.
Salama previously told The Drum that post-sale, the focus for Kantar will be on investing in technology that allows the business to work harder, better and faster for clients. A private equity sale, he believes, will see Kantar’s own model and processes evolve faster.
The sale is expected to go through in early 2020, subjected to approval from WPP's shareholders and government regulators.