Blackden will be responsible for developing and executing strategy throughout the Maxus network, and will be part of the WPP agency’s global management team.
He will work closely with Lindsay Pattison, the worldwide chief executive of Maxus, the regional chief executives and the executive committee to strengthen the agency’s challenger position and maintain its current momentum.
Blackden will also oversee Maxus’ creative tech division, Metalworks, with a focus on its positioning and output.
He will divide his time between London and New York.
Blackden was most recently at the tech business Device9, which he co-founded.
He said: "Media and technology are in my DNA, and the draw of Maxus and Group M was far too compelling for me to refuse."
Pattison called his appointment "a real coup".