Newland, who replaces Georgie Summerhayes, joins from MTV Networks Europe, where she was vice-president of international partnerships.
Newland will take up her new job in October. She will report to Summerhayes, who was promoted from chief executive of Stream\ to president of Stream\ International in May, when the agency expanded with the launch of Stream\ Asia Pacific.
Newland has been at MTV since 1998, working in the roles of European sponsorship manager and client services director.
While at the music broadcaster she worked with clients such as Nescafe, Daihatsu, Campari and Procter & Gamble. Before joining MTV, she was the sponsorship and promotions manager at Kiss FM.
Newland said: "I am thrilled to be joining such a creative and dynamic team and am looking forward to developing innovative brand entertainment solutions for current and future clients."
Summerhayes added: "We are very excited that Gemma is joining us at such an exciting time. She possesses a fantastically diverse set of skills and a great ambition to take Stream\ to new heights."
Mike Falconer and Summerhayes launched TBWA\Stream in the UK in 2001.