During Harris' time at Carat, he oversaw the agency network's digital capabilities and drove digital strategy and solutions for its global roster. Previously, he was AOL's international head of agencies, and IPG Mediabrands managing director of digital services.
Harris also either was a founder or co-founder a number of agencies, including both iProspect (at the time, called Diffiniti) and Mediacom North. Dell, Coca-Cola, Diageo, General Motors and Mastercard were among the global clients he has worked with in his 25-year career.
Harris said in a statement: "I have long been a big admirer of Mindshare and I am both excited and honoured to be able to join its management team and help write the next chapter in an already highly successful story."
Mindshare global chief executive Nick Emery added: "We’re delighted that James is joining us. The central question that all our clients face is uniting best in class performance skills with brand strategy to deliver a wholly integrated brand and performance approach marrying the best of both worlds. James is uniquely placed to lead that for us."
As GroupM has predicted online media consumption to eclipse linear TV viewership this year, Harris' hire has come at a moment when media planners need to address audiences drawn to a cord-cutting lifestyle.