Harwood-Matthews will take on the role as he aims to lead a new global business unit for the Infiniti account, run from the Los Angeles group TBWA\Chiat\Day.
Harwood-Matthews said: "I’m delighted to be invited to operate at this level and build a new global team for Infiniti.
"I’m also very proud of the fact that we have revitalised and built up a strong business in the North-West, drawing in new clients and talent to the region."
Harwood-Matthews will have the task of putting together a team who will have to come up with innovative creative work for the luxury car marque. He will report to John McNeel, the president of global clients.
Fergus McCallum, the former chief operating officer, steps in as the new chief executive of TBWA\Manchester as he prepares to lead the agency in a new direction.
McCallum said: "With a fantastic pool of talent and a truly integrated proposition that lives and breathes Disruption, we’re in a great position to continue TBWA\Manchester’s success story."