Pattison, who starts her new role immediately, has been the chief executive of Maxus in the UK since 2009 and will retain these duties while taking on global responsibilities.
The move follows last week's announcement that Vikram Sakhuja, currently the chief executive of Group M India and South Asia, will succeed Kelly Clark as the global Maxus chief executive later this year.
Pattison, who bolstered Maxus' UK management with the appointment of the managing director, Nick Baughan, from Mindshare in February, will continue to be based in London and will now take responsibility for the agency's global planning, data and insights, digital, marketing and new-business functions. She will also play a leading role in the agency's global client relationships, many of which are based in the UK.
Pattison said: "Leading Maxus in the UK has been incredibly fulfilling. We have enjoyed transformational growth and built a great team. I'm excited to help shape the Maxus offering and to drive success for our clients while still leading the UK agency."Follow @nickbatten2