Wilsher will assume the new role on 1 January and report to Carl Johnson, the founding partner and global chief executive. She will relocate to London.
Franke Rodriguez, partner and chief executive of Anomaly Toronto, will additionally run the New York office.
Wilsher will work on key global clients including Anheuser-Busch InBev, Converse, Diageo, Google and Hershey. Anomaly this year won a spot on the Beats By Dre creative roster in Los Angeles, London and Shanghai.
Wilsher has been tasked with "shaping the company’s global vision and execution" and supporting the London and Amsterdam businesses "within an expanded vision for Europe".
She joined Anomaly in 2010 after ten years at Fallon.
Johnson told Campaign: "We haven’t got a very good vision for Europe. We’ve got a sharp, strong vision for London and our Amsterdam hub, but we’ve never committed properly to a Europe-wide view. Karina will help drive that."