Warren has joined the Publicis Groupe-owned agency on a permanent basis after completing an eight-month consulting stint as chief digital officer at The Red Consultancy, which he joined after nearly eight years at Weber Shandwick.
He replaces Stanislas Magniant, who joined Coca-Cola as Northern European corporate comms director for digital strategies last month.
Stephanie Agresta, MSL’s global practice director, social media & digital, said Warren's hiring was part of a wider drive to expand the agency’s digital practice.
Pointing to other recent hires, including appointing Jon Chin to lead digital across Asia, she called growth in this area a "top priority".
Of Warren, she added: "He’s a rare mix of creative energy and digital expertise, something that is hard to find. The importance of creativity is growing and as well as bringing that to the table, he is also very entrepreneurial."
Highlighting its digital and marketing shop SAS in particular, Warren pointed to the "brilliant production capability" of MSL as one of his reasons for taking the job.
"MSL also has a great portfolio of clients, and the agency has a vision of genuinely creating a fully integrated digital content proposition," he added.
Red’s CEO Mike Morgan, meanwhile, added that Warren’s consultancy had given the agency a "blueprint for digital" that is set to lead to new hires and partnerships in the coming months.