There will be a transition from sister agency Maxus, ahead of the commencement of the contract in January 2018.
The agency will operate across BT’s sectors, consumer, EE, business and public sector, global services, wholesale and ventures, and Openreach.
Zaid Al-Qassab, chief brand and marketing officer at BT, said: “As a world-class communications company we need a world-class media approach to help us achieve and surpass our goals. Working with Essence will enable us to benefit from an industry-leading approach.”
Nick Baughan, incoming chief executive of Essence in EMEA, said: “BT has proven itself time and again to be a highly-regarded and forward-thinking client.
“With the right investment in data, analytics and measurement we can together create more value for BT and better experiences for consumers across all media.”
Maxus held the account since in 2010.