In his new role at the programmatic ad specialist he will be responsible for developing its product and data team as it aims to expand in Europe.
The team comprises 10 people across its European offices and is a key focus for growth, the company said.
Braun joins after 15 years at Publicis Groupe, Zenith’s parent company, where he had also served for two years as chief of staff for Maurice Lévy, the chief executive. He also created the social media video platform BlogBang.
Braun said: "It’s obvious the increasing role marketing technology platforms in today’s advertising ecosystem, so it’s extremely exciting to join a major differentiator like RadiumOne – notably helping brands unlock the value of what content is being shared online.
"I see my role as translating the intricacies of data and technology into the language that agencies and brands understand and speak."
Based in its Paris office, Braun will sit on RadiumOne's European executive board and report into the European managing director, Rupert Staines.
Staines said: "The marketing technology industry needs to be better at communicating to agencies how these technologies can help them execute campaigns more successfully for their clients.
"To attract someone of Julien’s talent and experience from one of the world’s largest agency groups is a clear indication of our burgeoning reputation.
"His switch is also affirmation of the increasing importance and relevance of data in the programmatic marketplace."
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