Reporting to Chris Weil, the chairman and chief executive of the network, he will be responsible for growing Momentum's business as well as working closely with MWG, which owns Momentum, to integrate the companies' offerings.
Before joining MWG, he was the EMEA new-business director at Abbott Mead Vickers BBDO.
Weil said: "Julian has never been the typical ad guy but is that rare breed that has also worked across multiple integrated marketing channels as well as design, relationship and the digital space."
Momentum Worldwide has 77 offices globally and works on live events, sponsorship, IP and content creation, music and entertainment marketing, and social media. In the UK, it has offices in London, Manchester and Cheshire.